Grassland Reclamation Research Articles

Reclamation of an eroded lakeshore slope using small vegetation islands and terraces

Bioengineering approaches to slope stabilization involve biological and mechanical methods with low impact on the environment and landscape. Slope stabilization using vegetation patches or islands can greatly decrease runoff and soil erosion on an eroded lake shore. While vegetation islands showed promise for forest and grassland reclamation, they have rarely been used on eroded lake shores. A study was conducted to determine whether bioengineering using native vegetation islands and terraces could successfully revegetate and stabilize a severely eroded lake shore slope in the central aspen parkland, Alberta, Canada. Three gullies and three slopes were terraced using pressure treated planks, then transplanted with non-dormant (mid-August) and dormant (mid-October) 20 cm diameter vegetation islands in a soil amended with 25% (by volume) compost. Volumetric water content was significantly less in lower slope positions than upper slope positions, and sediment transport to lower slope positions was much reduced. After one year, both non-dormant and dormant transplanted islands survived and established on the terraced slope, under relatively inhospitable growing conditions. Although non-dormant islands had significantly lower vegetation mortality (10% or less) than dormant islands on both slopes and gullies, no differences in health and vigour were found by the end of the study. Overall plant species number on the site increased during the study. Graminoid species densities increased, while those of forbs, shrub and tree species declined in the transplanted vegetation islands. Non-dormant islands had greater graminoid density than dormant islands, where Poa pratensis was the dominant species in the islands. Bioengineering with vegetation islands and terraces can assist in trapping runoff and sediment, and accelerate establishment of a diversity of plant species and groups relative to traditional revegetation methods.

Effects of different reclamation measures on soil quality restoration in open-pit mines: A meta-analysis based on the Chinese Loess Plateau

In the Loess Plateau region, ecological restoration projects have been implemented to restore the ecological environment of open-pit mines. However, no consistent conclusion has been reached regarding the response of soil remediation efforts to different ecological measures and restoration years. A meta-analysis was performed on the results of studies published over the past 30 years for open-pit mining areas on the Loess Plateau in China. The findings reveal that land rehabilitation considerably improved soil quality in open-pit mining areas on the Loess Plateau. Different ecological measures revealed a significant variability in soil quality restoration. Specifically, forestland reclamation affected soil organic matter and microbial carbon the most. Grassland reclamation substantially influenced soil total potassium, organic carbon, enzyme activity, and microbial abundance. Plowland caused the most effective improvement in soil total nitrogen and physical properties. However, total phosphorus and pH were unaffected by restoration measures. In addition, the period of land reclamation and soil nutrients showed a high correlation in the early stage of reclamation. After long-term reclamation, a decreased rate of soil quality improvement by remediation measures occurred after the soil quality returned to its premining level. A relatively lag was observed in the response of soil microbial indicators to environmental changes, and the premining level was reached after longer-term reclamation.

Seeding season and mowing affect native plant community development on reclaimed aspen parkland

ABSTRACT Land use intensification and rising production inputs continue to negatively affect many ecosystem services with significant challenges to restore these ecosystem services in the disturbed landscape. Using native species to revegetate disturbed ecosystems continues to gain momentum. An understanding of the role of seeding season and mowing in native plant community development is required to improve reclamation success. Research using 20 native grasses and forbs was conducted to determine how seeding season (fall, spring) and mowing (mowed, unmowed) influenced revegetation of grassland reclamation sites in Alberta, Canada. Species density, biovolume, richness and ground cover were assessed over two growing seasons. Density, biovolume and species richness of seeded grasses and forbs were generally higher in spring than fall seeded treatments, whereas non-seeded grasses and forbs were lower in spring seeded treatments. During the first growing season, mowing increased seeded species density and biovolume and decreased non-seeded species biovolume, with no effect on seeded species in the second growing season. Mowing and fall seeding decreased bare ground in the second growing season. The outcomes of this study suggest grasses and forbs were more successful when spring seeded versus fall seeded, and beyond the first growing season the influence of mowing was negligible.

Changes in soil fertility and microbial communities following cultivation of native grassland in Horqin Sandy Land, China: a 60-year chronosequence

BackgroundGrassland conversion to cropland is a prevailing change of land use in traditionally nomadic areas, especially in the Mongolian Plateau. We investigated the effects of grassland conversion followed by continuous cultivation on soil properties and microbial community characteristics in Horqin Sandy Land, a typical agro-pastoral transition zone of Northern China. Soil samples were collected from the topsoil (upper 20 cm) across a 60-year cultivation chronosequence (5, 15, 25, 35 and 60 years) and unconverted native grassland. Soil physico-chemical properties were determined and high-throughput sequencing was used to assess microbial community diversity and composition.ResultsGrassland cultivation resulted in changes to soil properties in both the short and longer term. Initially, it significantly increased soil bulk density (BD), electrical conductivity (EC), soil total nitrogen (TN), available phosphorus (AP) and available potassium (AK) concentrations, while reducing soil water content (SWC) and soil organic carbon content (SOC). Over the next 35–55 years of continuous cultivation, the trend for most of these characteristics was of reversion towards values nearer to those of native grassland, except for SOC which remained highly depleted. Cultivation of grassland substantially altered soil microbial communities at phylum level but there was no significant difference in microbial α-diversity between native grassland and any cropland. However, soil bacterial and fungal community structures at phylum level in the croplands of all cultivation years were different from those in the native grasslands. Heatmaps further revealed that bacterial and fungal structures in cropland tended to become more similar to native grassland after 15 and 25 years of cultivation, respectively. Redundancy analysis indicated that SOC, EC and BD were primary determinants of microbial community composition and diversity.ConclusionsThese findings suggest that agricultural cultivation of grassland has considerable effects on soil fertility and microbial characteristics of Horqin Sandy Land. Intensive high-yield forage grass production is proposed as an alternative to avoid further native grassland reclamation, while meeting the grazing development needs in the ethnic minority settlements of eco-fragile regions.

Changes in soil organic carbon and its fractions under grassland reclamation in alpine-cold soils, China

Grasslands are the main land use types in China, but their reclamation into croplands can influence the terrestrial carbon and, consequently, impact the global carbon balance. The long-term reclamation of alpine-cold grasslands to croplands are expected to decrease the soil organic carbon (SOC) and its fractions. Here, we conducted an in situ systematic study to measure the SOC and its fraction in soils sampled in an alpine-cold grassland with a gradient of cultivation history from 0 to 40 years. The SOC and its fractions significantly decreased after reclamation (P < 0.05), and the changes in the 0–20 cm soil layer were the greatest among the three sampling depths. After 40 years of reclamation, the SOC content and storage at 0–20 cm decreased by 74 and 60%, respectively. The decreases in the soil labile carbon fractions were more rapid and apparent than the SOC, especially the particular organic carbon (POC), which decreased by 82%. The soil humus carbon fractions also decreased, particularly the humic acid carbon (HAC), which decreased by 81%. The reduction rates of SOC and its fractions gradually decreased with an increase in the cultivation history. Besides, the ratios of the optical densities or absorbances of humic acid (HA) and fulvic acid (FA) solutions at 465 and 665 nm (E<sub>4</sub>/E<sub>6</sub> ratios) and the hue coefficient (Δlog K values), which is the logarithm disparity between the 400 and 600 nm absorbance of the HA (FA) substance, in the solution gradually decreased, indicating that the quality of the soil humus decreased. The reclamation significantly decreased the SOC and its fractions in the alpine-cold soils, which should not be underestimated in the impact on the terrestrial carbon cycles and balance in the long run.

Long-term cultivation alter soil bacterial community in a forest-grassland transition zone.

Changes in land use types can significantly affect soil porperties and microbial community composition in many areas. However, the underlying mechanism of shift in bacterial communities link to soil properties is still unclear. In this study, Illumina high-throughput sequencing was used to analyze the changes of soil bacterial communities in different land use types in a forest-grassland transition zone, North China. There are two different land use types: grassland (G) and cultivated land (CL). Meanwhile, cultivated land includes cultivated of 10 years (CL10) or 20 years (CL20). Compared with G, CL decreased soil pH, SOC and TN, and significantly increased soil EC, P and K, and soil properties varied significantly with different cultivation years. Grassland reclamation increases the diversity of bacterial communities, the relative abundance of Proteobacteria, Gemmatimonadetes and Bacteroidetes increased, while that of Actinobacteria, Acidobacteria, Rokubacteria and Verrucomicrobia decreased. However, the relative abundance of Proteobacteria decreased and the relative abundance of Chloroflexi and Nitrospirae increased with the increase of cultivated land years. Mantel test and RDA analysis showed that TP, AP, SOC and EC were the main factors affecting the diversity of composition of bacterial communities. In conclusion, soil properties and bacterial communities were significantly altered after long-term cultivation. This study provides data support for land use and grassland ecological protection in this region.

Spatio-temporal patterns of oasis dynamics in China’s drylands between 1987 and 2017

Oases are among the most productive and vulnerable ecosystems on drylands as well as central areas of human life and economic development. In China, oasis expansion and degradation are directly related to the survival and development of tens of millions of inhabitants who live within them, profoundly affecting human well-being. However, our understanding of the spatiotemporal dynamics of China’s oases has been limited. This creates a challenge to accurately assess the environmental impacts of oasis dynamics and sustainable oasis development. Here we analyzed Landsat images (5 TM, 7 ETM+, and 8 OIL, ∼61 900 images) over the period 1987–2017, and we produced annual maps of China’s oases (30 m spatial resolution) using trajectories and spectral-temporal segmentation algorithm (LandTrendr) and machine-learning methods (Random Forest). We found that oasis areas increased significantly between 1987 and 2017 (+8.82 Mha). Grasslands and croplands expanded the most, and reclamation of deserts and grasslands made cropland the largest gainer. At the provincial scale, oasis expansion in Inner Mongolia and Qinghai was mainly attributed to grassland restoration. In Xinjiang, Gansu, and Ningxia, reclamation of croplands was also an important factor in addition to grassland restoration. With the expansion of the oasis ∼73.36% of areas showed decreasing trends of soil moisture, and even desertification in some areas. The overexpansion of oases might cause a great challenge to regional water security. Our dataset and results can provide a basis for identifying trade-off areas/regions between development benefits and environmental impacts, helping policymakers to identify high-priority areas for intervention and reasonably plan land-use spatial structure in oasis areas for sustainable development of oases.

Quantifying impacts of climate and human activities on the grassland in the Three-River Headwater Region after two phases of Ecological Project

The Three-River Headwater Region (TRHR) of China is a typical representative of the alpine environment in the Central Asian plateau and the alpine grassland in the world. Grassland degradation is one of its serious ecological problems. The purpose of this study is to quantify the joint impacts of climate and human activities on grassland changes in TRHR after two phases of Ecological Conservation and Construction Project (Ecological Project). Grassland vegetation coverage is selected as an indicator for analyzing grassland changes. We adopt Sen+Mann-Kendall trend analysis, residual trend analysis and correlation analysis methods to analyze the trends in spatial-temporal changes and driving factors of grassland in TRHR from 2000 to 2019. The results show that: (1) The grassland has been mainly restored, and the degraded grassland area only accounts for 1.66% of TRHR. After the implementation of the first phase of the Ecological Project, the percentage of restored grassland area has significantly increased from 8.82% to 24.57%, and slightly decreased during the second phase. (2) The establishment of national nature reserves and the implementation of the Ecological Project have changed the situation that “the grassland inside the reserve is worse than that outside the reserve”. (3) Grassland restoration is mainly affected by the joint effects of climate and human activities. Nevertheless, grassland degradation is mainly affected by human activities such as overgrazing and grassland reclamation. All of these findings can enrich our understanding of grassland restoration in TRHR. Artificial measures have certain limitations in promoting grassland restoration. Natural restoration should be considered when human beings strengthen ecological conservation and transform their production and life styles.

Grassland reclamation of a copper mine tailings facility: Long‐term effects of biosolids on plant community responses

AbstractAimWe explore long‐term plant community responses 17 years after a one‐time application of biosolids (0, 50, 100, 150, 200, 250 dry Mg/ha) to determine: (a) whether the land application of biosolids on mine tailings, seeded with an agronomic grass‐legume mixture, affects long‐term plant community responses; (b) how application rates and soil texture influenced plant community responses and community structure; and (c) whether native plant species have colonized and contributed to the reclaimed plant community.LocationTwo tailings deposits (sand and silt loam) generated by a copper–molybdenum (Cu–Mo) mine in southern British Columbia, Canada.MethodsPlant communities were sampled by visual evaluation of cover percentage to the lowest taxonomic level possible. Vegetation surveys were completed on two mine tailings deposits within the storage facility that have different soil textures (sand and silt loam).ResultsResults showed that the interaction of biosolids applications and soil texture impacted multiple community plant responses, including increasing plant cover at both sites, and increasing richness, evenness and diversity at the sandy site. Biosolids application enhanced the performance of spontaneously established species (volunteer species) and non‐native/naturalized grasses.ConclusionOur study demonstrated that biosolids application facilitates ecological succession by enhancing the establishment of non‐native volunteer species over the long term, which increases vegetative cover on both deposits and promotes plant communities’ diversity on sites with sandy soil texture.

Impact of Cropland Evolution on Soil Wind Erosion in Inner Mongolia of China

Understanding soil erosion responses to cropland expansion/shrinking plays a crucial role in regional agriculture sustainability development in drylands. We selected Inner Mongolia, a typical water resource constraints region with acute cropland expansion, as the study area in China. Spatial cropland evolution and its impact on wind-driven soil erosion were investigated with the help of field sampling data, remotely sensed retrieved data, and the revised wind erosion model (RWEQ). Results showed that the cropland area of Inner Mongolia presented an increased growth trend, with a net increase area of 15,542.9 km2 from 1990 to 2018. Cropland characteristics in Inner Mongolia presented continuous growth in its eastern region, basically constant growth in its central region, and declined in its western region. Most cropland declines occurred after 2000 when the Grain for Green project began, which means that acute cropland expansion happened from 1990 to 2000. The soil wind erosion modulus showed a net increase with cropland expansion. The reclamation of forests and grasslands contributed to an increase of 5.0 million tons of the soil wind erosion modulus, 80% of which was produced in the eastern part of the region. The conversion from croplands to grasslands/forests caused a decrease of approximately 2.7 million tons, 62% of which was in the east and 25% in the west of the region. Considering the constraints of water shortage and over-exploitation of groundwater, we provide a path based on a balance between ”resource-production-ecosystem” to achieve ecologically sustainable agriculture development in the drylands of China.

Grassland ecological restoration based on the relationship between vegetation and its below-ground habitat analysis in steppe coal mine area.

Coal mining activities have caused severe disturbances to the regional ecosystem and soil properties. Studying the relationship of vegetation and its below-ground habitat (RVBGH) is of great significance to the coal mine land ecological restoration. To identify the optimal thickness of the soil layer for mine land ecosystem recovery and characterize the changes of the reclaimed soil-vegetation ecosystem, we studied natural and reclaimed grassland at the coal mine of Baorixile, located in Hulunbuir Steppe, Northeastern China. The vegetation and its below-ground habitat (BGH), including "root mass" and soil properties in the soil profile (0-100cm), were surveyed in the natural and different year-reclaimed grassland. The "root mass" is the part of root system that has the most amounts of root hairs, which is the functional zone for plant growth. The RVBGH was identified by the "root mass" and plant water extraction depth, measured through the isotope δD and δ18O method. Firstly, the BGH of natural grassland was identified as a "double layer" vertical structure, with the "root mass" of 37.11±2.57% fine roots at 0-20cm range and 30.44±2.67% at 20-40cm range. The annual and perennial plant "root mass" was found at 0-20cm and 20-40cm depth, respectively. Secondly, an optimal thickness of the soil covering of 30-40cm was proposed for grassland reclamation. Thirdly, along the reclamation chronosequence, the values of the reclaimed vegetation properties (height, density, coverage and diversity) increased and a deep root system was established. The "root mass" increased from one layer to double layer and the amount of total fine roots increased from 1621±231.9 to 4459±456.0. Moreover, the reclaimed soil properties of organic matter, cation exchange capacity, available N and P also increased. The study proposed that vegetation restoration was significantly correlated with its BGH, suggesting that vegetation BGH recovery is crucial in ecological restoration.

Revegetation of degraded ecosystems into grasslands using biosolids as an organic amendment: A meta‐analysis

AbstractQuestionsBiosolids are a source of nutrient‐rich organic material that can be used to improve degraded or disturbed soils. Research on vegetation responses to the land application of biosolids has increased in the past 20 years, but there is no consensus on how plant communities respond to biosolids applications. What factors influence productivity and vegetative cover following biosolids application for grassland reclamation? How does the addition of biosolids impact plant community responses?LocationGlobal, but predominantly North America and Europe.MethodsTo explore vegetative responses following biosolids application, we used a global systematic review and meta‐analysis of 59 articles. Our meta‐analysis used the log response ratio (LRR) as an effect size for productivity, total cover, species richness, diversity and exotic species abundance and explored covariates addressing various site characteristics and reclamation strategies.ResultsWe found that across sites, the land application of biosolids significantly increased productivity and cover but had no significant overall effect on species richness, Shannon diversity or exotic species abundance on degraded lands. These increases in the LRR for productivity and vegetative cover were lower on sites that experienced a fire prior to biosolids application. Climatic variables like mean annual temperature were shown to alter the response of vegetative cover, where warmer sites tended to have more positive responses to biosolids. Seeding was found to increase plant cover but decrease species richness early in the reclamation process.ConclusionsThis area of research is growing; most of the publications we used come from the last 20 years and were mostly conducted in North America and Europe. While we can build on the present literature, there is clearly room for more research to ensure the process of reclaiming degraded ecosystems using biosolids results in desired plant communities, e.g. high native species diversity. Future research should consistently report biosolids chemical characteristics as well as application and processing methodologies.

Hydrologic modeling to examine the influence of the forestry reclamation approach and climate change on mineland hydrology

Forests in the Appalachian region of the U.S. are threatened by a variety of short- and long-term pressures, including climate change, invasive species, and resource extraction. Surface mining for coal is one of the most important drivers of land-use change in the region, reducing native forest cover, causing forest fragmentation, eliminating intact soil, and affecting water resources. The Forestry Reclamation Approach (FRA) has been demonstrated as a successful best practice for restoring forests on mine-impacted landscapes, but little information exists on how the practice will affect hydrologic processes. A study was initiated to examine soil-water movement, as in-situ saturated hydraulic conductivity (Ksat), combined with soil porosity to quantify the potential influence on streamflow of reclaimed mines relative to an unmined, forested control site in eastern Kentucky. We compared different reclamation techniques and time since reclamation to determine the extent to which hydrologic function can be restored. We also simulated evapotranspiration at the watershed scale as a function of reclamation technique for both historical and projected (2050) climate. Results indicate that conventional grassland reclamation critically changes how soil water transitions to streamflow, primarily due to Ksat variability that exceeds that measured for intact and FRA soils. Sites reclaimed using FRA exhibited a soil-water environment that was more similar to the unmined control. However, all reclaimed mine soils were thinner, retained and stored less soil water, and thus could provide less plant-available water during the growing season. The plant-available water stored in reclaimed landscapes may not be sufficient to support forest health and this is exacerbated by projected climate conditions. However, soil development under a combination of FRA techniques has the potential to mitigate this limitation.

Changes of soil organic carbon stocks from the 1980s to 2018 in northern China’s agro-pastoral ecotone

Soil carbon sequestration and potential sequestration are key issues in global carbon research, as the size of the soil organic carbon (SOC) stocks and their changes over time are important for understanding their role in climate change. In northern China’s agro-pastoral ecotone, we compared SOC data derived from 238 sampling sites during China’s National Soil Inventory in the 1980s with the results of field surveys at 644 sites in 2018 to calculate the changes in SOC stocks between the 1980s and 2018. We found that the mean SOC stock to a depth of 30 cm decreased significantly, from 4.48 kg C m−2 in the 1980s to 3.60 kg C m−2 in 2018, and the total SOC stock decreased from 2793.17 Tg to 2248.34 Tg. This amounted to an average decrease of 27.74 g C m−2 yr−1 over the 30-year study period. Furthermore, we used a land use and cover change transition matrix to quantify the amount of SOC change caused by these transitions; the SOC reduction could be mainly ascribed to overgrazing, grassland reclamation for agriculture, and grassland desertification. Large-scale ecological restoration projects have increased SOC reserves, but not enough to compensate for the loss of SOC caused by factors such as desertification and ecosystem degradation. We also performed regression analysis for the relationship between the change in the SOC stock and the rates of temperature and precipitation change. We found that increasing temperature non-significantly decreased SOC, whereas precipitation was significantly (P < 0.05) related to SOC change, but the R2 was very low (0.01). Our analysis suggests that humans have affected SOC in northern China’s agro-pastoral ecotone more strongly than climatic factors.

Changes in soil properties and crop yields of farmland over a 20-year reclamation period from grassland in the hilly areas of Hebei, China

ABSTRACT We investigated the effects timing after reclamation with imported soil on soil organic carbon (SOC), total nitrogen (TN), aggregates, and crop yield of farmland converted from grassland. Soil samples collected in farmland plots after 1, 3, 6, 10, 15, and 20 years of reclamation were ananlysed. Maize yield was also measured. The SOC and TN content slightly decreased initially, and then increased up to their grassland levels in 20 years. The SOC and TN content of the 20-year reclaimed farmland increased by 168% and 103%, respectively, compared with that in 1-year reclaimed farmland in the 0–10 cm soil layer. It improved over reclamation years compared with that in the imported soil. Over time, macroaggregate proportion in the 0–10 cm layer decreased by 8%, whereas that in the 10–20 cm and 20–40 cm increased by 3% and 13%, respectively. The grassland had higher water stability of developed aggregates than the farmland. The maize yield initially increased and plateaued after 15 years. Overall, grassland reclamation to cropland through imported soil engineering alters soil properties, such as SOC, TN, and soil water stability, they initially decreased and subsequently stabilized after 10 reclamation yeas.

Detecting Vegetation Variations and Main Drivers over the Agropastoral Ecotone of Northern China through the Ensemble Empirical Mode Decomposition Method

Vegetation is the major component of the terrestrial ecosystem. Understanding both climate change and anthropogenically induced vegetation variation is essential for ecosystem management. In this study, we used an ensemble empirical mode decomposition (EEMD) method and a linear regression model to investigate spatiotemporal variations in the normalized difference vegetation index (NDVI) over the agropastoral ecotone of northern China (APENC) during the 1982–2015 period. A quantitative approach was proposed based on the residual trend (RESTREND) method to distinguish the effects of climatic (i.e., temperature (TEM), precipitation (PRE), total downward solar radiation (RAD), and near surface wind speed (SWS)) and anthropogenic effects on vegetation variations. The results showed that the NDVI exhibited a significant greening trend of 0.002 year−1 over the entire study period of 1982–2015 and that areas with monotonous greening dominated the entire APENC, occupying 40.97% of the region. A browning trend was also found in the central and northern parts of the APENC. PRE presented the highest spatial correlation with the NDVI and climate factors, suggesting that PRE was the most important factor affecting NDVI changes in the study area. In addition, the RESTREND results indicated that anthropogenic contributions dominated the vegetation variations in the APENC. Therefore, reusing farmland for grass and tree planting made a positive contribution to vegetation restoration, while deforestation, overgrazing, and the reclamation of grasslands were the opposite. In addition, with the continuous implementation of national ecological engineering programs such as the Grain to Green Program, positive human activity contributions to vegetation greening significantly increased. These results will support decision- and policy-making in the assessment and rehabilitation of ecosystems in the study region.

Monitoring grassland reclamation in the Mu Us Desert using remote sensing from 2010 to 2015

New conversion from grassland to cropland was effectively curbed with the implementation of the Grain-to-Green Program (GTGP) in northern China from 1999 to 2010. However, the phenomenon of grassland reclamation has significantly increased since 2010. Here, the latest trend of conversion from grassland to cropland was evaluated using a Landsat dataset from 2010 and 2015 in the Mu Us Desert (MUD) of northern China. An object-based approach was chosen to classify grassland and farmland information, and the classification accuracy was 98.33% based on 120 cropland verification points, which were obtained through available Google Earth and field survey data. The area of grassland reclamation increased by 411.29 km2 from 2010 to 2015 and was mainly distributed in the southeastern and southwestern parts of the MUD, accounting for 9.78% of the total cropland area in 2015. There were two ways to reclaim grassland, including herdsmen cultivating grasslands on their own pastures and grassland reclamation projects implemented by enterprises under the direction of local governments. Exposed cultivated land is more susceptible to wind erosion and eventually leads to decreasing agricultural productivity and desertification. Therefore, strategies to reduce wind erosion on reclaimed grassland in the study area should be implemented as soon as possible, including several alternative cultivation systems and ridge tillage. If conditions permit, conservation tillage should be changed in the MUD.

Early growth pattern of &lt;i&gt;Miscanthus sinensis&lt;/i&gt; and two subordinate species in nutrient-poor soil as a key issue for the restoration of &lt;i&gt;M. sinensis&lt;/i&gt; community

There were few researches in Japan on revegetation techniques for the restoration or reclamation of semi-natural grasslands. Miscanthus sinensis is a major dominant species in the Japanese semi-natural grasslands, which sometimes produces species-rich plant communities. The present study aimed to describe the early stage of growth patterns in M. sinensis and two subordinate species, Aster microcephalusand Potentilla freyniana, taking competitive interaction for light into account. We made a one-year pot experiment observing the growth of the subordinate species surrounded by pots with M. sinensis with and without fertilizer input in a hexagonal design. Results showed that M. sinensis in unfertilized pots failed to establish closed canopy within a single season. M. sinensis in fertilized pots had quarto biomass compared with that in unfertilized M. sinensis. Relative photosynthetic photon flux density at the ground level was 20% after one and a half month onwards after establishment. P. freyniana significantly decreased biomass due to its low statue by the severe shade of M. sinensis compared with those in unfertilized treatment, while A. microcephalus did not decrease the biomass escaping from shade by developing leaves at vertically higher position than that in unfertilized treatment. Possibility for the persistence of subordinate species under the predominance of M. sinensis with or without fertilizer input was further discussed.

Managed grassland alters soil N dynamics and N2O emissions in temperate steppe

Reclamation of degraded grasslands as managed grasslands has been increasingly accelerated in recent years in China. Land use change affects soil nitrogen (N) dynamics and nitrous oxide (N2O) emissions. However, it remains unclear how large-scale grassland reclamation will impact the grassland ecosystem as a whole. Here, we investigated the effects of the conversion from native to managed grasslands on soil N dynamics and N2O emissions by field experiments in Hulunber in northern China. Soil (0–10cm), nitrate (NO3−), ammonium (NH4+), and microbial N were measured in plots in a temperate steppe (Leymus chinensis grassland) and two managed grasslands (Medicago sativa and Bromus inermis grasslands) in 2011 and 2012. The results showed conversion of L. chinensis grassland to M. sativa or B. inermis grasslands decreased concentrations of NO3−–N, but did not change NH4+–N. Soil microbial N was slightly decreased by the conversion of L. chinensis grassland to M. sativa, but increased by the conversion to B. inermis. The conversion of L. chinensis grassland to M. sativa (i.e., a legume grass) increased N2O emissions by 26.2%, while the conversion to the B. inermis (i.e., a non-legume grass) reduced N2O emissions by 33.1%. The conversion from native to managed grasslands caused large created variations in soil NO3−–N and NH4+–N concentrations. Net N mineralization rates did not change significantly in growing season or vegetation type, but to net nitrification rate. These results provide evidence on how reclamation may impact the grassland ecosystem in terms of N dynamics and N2O emissions.

Relative performance of native cultivar and wild collected seed for grassland restoration

Availability of native plant materials for grassland restoration is limited. Even when available in sufficient quantities for ecological restoration projects, seed germination and establishment in relatively arid environments is often low. Poor revegetation results in soil erosion, invasion by non-native plant species and reduced aesthetics. Therefore, development and use of native plants bred for traits favourable for restoration should be considered. This study addressed whether native cultivar seed, commercially selected for advantageous growth characteristics, could improve native grass species reestablishment relative to wild collected seed. Cultivar and wild seed types of four cool season native grass species were investigated at three foothills fescue grassland reclamation sites: Bromus carinatus (mountain brome), Elymus trachycaulus (slender wheatgrass), Festuca idahoensis (Idaho fescue) and Koeleria macrantha (June grass). Seeding and transplanting were conducted and germination, emergence, density, height and health were determined from 2011 to 2013. No significant differences were detected between cultivar and wild seed types except laboratory germination, which was greater in the Elymus trachycaulus cultivar and in the wild collected Koeleria macrantha. Bromus carinatus performed poorly as a seedling from either seed type. Consistent trends in cultivar and wild seed performance, that reflected seed germination, were found for each species although results were not significant due to high variability. Results show that for these common grass species, seed type may not influence initial establishment. Differences among species were significant and varied with response measured, suggesting species characteristics are a key factor affecting native grass reestablishment. Species specific responses to seed type highlight the importance of making seed source decisions on a species basis.