Temperate Grassland Research Articles

Disruption of fungal hyphae suppressed litter-derived C retention in soil and N translocation to plants under drought-stressed temperate grassland

Litter decomposition often represents the largest carbon (C) and nitrogen (N) input into the soil and thereby supports soil nutrition cycling function. Common mycelial networks (CMNs) can promote soil C and N trades during the litter decomposition process. However, the degree to which this promotion depends on abiotic variables, such as drought, remains unresolved. Importantly, the influence of soil fungi mycelium on the turnover of litter-derived C and N could weaken under drought if disrupts fungal hyphae. Here, we used plant litter of stable isotope dual-labeling (13C and 15N), experimental drought (ambient, 30%, 50%, or 70% growing season precipitation reductions), and physical disruption to soil fungal hyphae (via soil core rotation) to investigate decomposition dynamics along the soil-plant-atmosphere continuum in a temperate grassland. On average, drought significantly slowed plant litter decomposition by up to 31.8%, but undisrupted fungal hyphae accelerated litter decomposition by up to 31.7% and promoted the release of C and N from plant litter. The intactness of fungal hyphae would have divergent effects on the allocation of litter-derived C and N during decomposition under drought conditions. Intact soil fungal hyphae contributed about 47% of litter-derived C transfer into soil microbial biomass after litter decomposition, but no significant effects in the soil, plant aboveground, or CO2 emissions, compared to hyphae disruption treatment. Undisrupted hyphae promoted approx. 82% of the turnover of litter-derived N from soil to plant and reduced content of litter-derived N in soil and N2O emission compared to hyphae disruption. We conclude that intact networks of soil fungal hyphae are essential to maintaining litter decomposition processes under drought conditions in temperate grassland ecosystems because the fungi promote releases of carbon and nitrogen from plant litter that facilitate carbon and nitrogen cycling.

Responses of net ecosystem carbon budget and net global warming potential to long-term nitrogen deposition in a temperate grassland

Grassland systems are important terrestrial carbon sinks and have great potential for carbon (C) sequestration. Increased atmospheric nitrogen (N) deposition has profoundly affected C balance and greenhouse gas emissions in grassland systems. However, the effects of long-term nitrogen (LN) deposition on net ecosystem carbon budget (NECB) and net global warming potential (NGWP) in grassland systems are still not clearly understood. A field experiment was conducted to test the effect of LN addition (0, 30, 60, 120 and 240 kg N ha−1 yr−1) on NECB and NGWP in a temperate grassland area in Inner Mongolia, China. LN addition significantly increased soil organic carbon density (SOCD) and C sequestration in surface soil (0–30 cm) with the increase of N addition rate from 2005 to 2018. In contrast, a decrease in ecosystem respiration (Re) was observed, except at low LN concentration (30 kg N ha−1 yr−1). Annual N2O flux was significantly increased, and the CH4 sink was significantly decreased by LN addition. NECB and NGWP were relatively weak in this temperate grassland, ranging from −627.29 ± 198.81 and −232.87 ± 23.11 kg CO2 ha−1yr−1, respectively, and significantly decreased with increasing LN application. The offset effect of N2O emission to ecosystem C uptake decreased significantly with increased LN addition, and was stable at high LN addition. This was related to the increase in soil C sequestration due to plant C uptake. These results indicate that LN addition significantly decreased the NECB and NGWP of this grassland. Increased long-term N deposition significantly enhanced soil C sequestration, which has important implications for mitigating climate warming.

The effect of charcoal production on carbon cycling in African biomes

AbstractUsing biomass for charcoal production in sub‐Saharan Africa (SSA) may change carbon stock dynamics and lead to irreversible changes in the carbon balance, yet we have little understanding of whether these dynamics vary by biome in this region. Currently, charcoal production contributes up to 7% of yearly deforestation in tropical regions, with carbon emissions corresponding to 71.2 million tonnes of CO2 and 1.3 million tonnes of CH4. With a projected increased demand for charcoal in the coming decades, even low harvest rates may throw the carbon budget off‐balance due to legacy effects. Here, we parameterized the dynamic global vegetation model LPJ‐GUESS for six SSA biomes and examined the effect of charcoal production on net ecosystem exchange (NEE), carbon stock sizes and recovery time for tropical rain forest, montane forest, moist savanna, dry savanna, temperate grassland and semi‐desert. Under historical charcoal regimes, tropical rain forests and montane forests transitioned from net carbon sinks to net sources, that is, mean cumulative NEE from −3.56 ± 2.59 kg C/m2 to 2.46 ± 3.43 kg C/m2 and −2.73 ± 2.80 kg C/m2 to 1.87 ± 4.94 kg C/m2 respectively. Varying charcoal production intensities resulted in tropical rain forests showing at least two times higher carbon losses than the other biomes. Biome recovery time varied by carbon stock, with tropical and montane forests taking about 10 times longer than the fast recovery observed for semi‐desert and temperate grasslands. Our findings show that high biomass biomes are disproportionately affected by biomass harvesting for charcoal, and even low harvesting rates strongly affect vegetation and litter carbon and their contribution to the carbon budget. Therefore, the prolonged biome recoveries imply that current charcoal production practices in SSA are not sustainable, especially in tropical rain forests and montane forests, where we observe longer recovery for vegetation and litter carbon stocks.

Responses of bud banks and shoot density to experimental drought along an aridity gradient in temperate grasslands

Abstract Climate change is expected to increase the magnitude and frequency of extreme drought in most grassland ecosystems. Exploring the responses of below‐ground bud banks and their relationships with above‐ground plant structure and drought is need to explain how climate change will impact grassland ecosystems. However, studies on the response of community‐scale bud and shoot densities to experimental drought along an aridity gradient are rare. We experimentally removed 66% of growing season precipitation for 4 years in three temperate grasslands that spanned an aridity gradient in northern China. We quantified the legacy effects of drought on grass, forb and total community below‐ground bud density, above‐ground shoot density and the ratio of bud to shoot density 1 year following treatment. Below‐ground bud density was lowest at the highest aridity site for the entire community, while above‐ground shoot density was highest at the medium aridity site. Below‐ground bud and above‐ground shoot densities were the lowest at the high aridity site for grasses but the highest for forbs at this site. Bud:shoot ratios decreased with increasing aridity for grasses, yet remained constant for forbs along the aridity gradient. Below‐ground bud density in drought plots remained lower than controls a year following drought at each site. Experimental drought did not alter the below‐ground bud bank for grasses but decreased forb bud banks across sites. Experimental drought had little legacy effects on above‐ground shoot density and bud:shoot ratios for grasses, forbs and the total community at each site. Our results suggest that grass and forb bud banks can differ in their responses to both multi‐year drought along an aridity gradient, and that bud limitation for shoot generation may increase as grasslands get drier. Bud bank responses to climate will impact plant community functioning and resilience. Thus, incorporating bud bank dynamics will improve projections of grassland ecosystems under future climate change. Read the free Plain Language Summary for this article on the Journal blog.

The quality and quantity of SOM determines the mineralization of recently added labile C and priming of native SOM in grazed grasslands

Continuous and pulsed inputs of labile organic carbon (LOC) into soil are common. However, because soil microbial responses to LOC input are rapid, the relative contributions of respiration derived from LOC to total microbial respiration and their influencing factors remain elusive. Furthermore, although numerous studies have explored the priming effect (PE) of soil organic matter (SOM) mineralization induced by LOC addition, few studies have focused on its short-term effects. There are some indications that the response of soil microbes to LOC input depends on the microbial demand of nutrients, especially C and N. Therefore, variations in soil C and N characteristics may further influence microbial response processes to LOC inputs and the decomposition of LOC and SOM, but a comprehensive understanding of this is lacking. To address this gap, 13C-labeled glucose was added to six temperate grassland soils with different C/N ratios (9.98–12.0), which were collected from areas with different grazing exclusion durations and at different soil depths. The microbial respiration was measured at 9-min intervals across a 105-h period. We found that soil microbes responded rapidly to LOC input, and microbial biomass controlled by soil organic C (SOC) and C/N was the most important factor directly influencing the intensity of the microbial response to LOC input. Grazing and deeper soil layers decreased the respiration derived from LOC and their relative contribution to total respiration, mainly attributed to variations in soil C/N and fungal/bacterial ratio (Fu/Ba). LOC addition stimulated SOM decomposition in all soils and increased respiration of SOM by 11.3–92.4 mg C/g SOC, equivalent to 18.7–266.1 % priming. Grazing and increased soil depth resulted in a greater PE and soil C loss, with soil C/N and SOC content being the most important regulators. Overall, this study revealed the important influence of LOC on soil C fluxes and highlighted the important role of SOM quality and quantity in regulating grassland soil C cycling.

Comparing process-based models with the inventory approach to predict CH4 emission of livestock enteric fermentation

Livestock production is the largest anthropogenic methane (CH4) source globally over the decades. Enteric fermentation of ruminants is responsible for the majority of global livestock CH4 emissions. Both inventory-based models (IvtMs) and process-based models (PcMs) are extensively used to assess the livestock CH4 emission dynamics. However, the model performance and the associated uncertainty have not been well quantified and understood, which greatly hamper our credibility of the regional and global CH4 emission predictions. In this study, we compared the CH4 emissions of livestock enteric fermentation (CH4,ef) predicted by multiple IvtMs and PcMs across Inner Mongolia, a region dominated by typical temperate grasslands that are widely used for animal husbandry. Twenty predictions from five IvtMs, and ten predations from five PcMs were explicitly calculated and compared for the reference year of 2006. The CH4,ef predicted from PcMs is lower than IvtMs and the variation between PcMs is substantially higher, i.e. 0.34 ± 0.36 g CH4/m2yr and 0.78 ± 0.14 g CH4/m2yr for PcMs and IvtMs, respectively. Different model strategies undertaken, i.e. the demand-oriented strategy for IvtMs and the resource-demand co-determined one for PcMs, cause the different predictions of CH4,ef between the two model groups. Using the results from IvtMs as the baseline scalar, we identified and benchmarked the performance of individual PcMs in the study region. The quantitative information provided can facilitate the understanding of key principles and processes of CH4,ef estimations, which will contribute to the future model development of global CH4 emission.

Intensification differentially affects the delivery of multiple ecosystem services in subtropical and temperate grasslands

Intensification, the process of intensifying land management to enhance agricultural goods, results in “intensive” pastures that are planted with productive grasses and fertilized. These intensive pastures provide essential ecosystem services, including forage production for livestock. Understanding the synergies and tradeoffs of pasture intensification on the delivery of services across climatic regions is crucial to shape policies and incentives for better management of natural resources. Here, we investigated how grassland intensification affects key components of provisioning (forage productivity and quality), supporting (plant diversity) and regulating services (CO2 and CH4 fluxes) by comparing these services between intensive versus extensive pastures in subtropical and temperate pastures in the USDA Long-term Agroecosystem Research (LTAR) Network sites in Florida and Oklahoma, USA over multiple years. Our results suggest that grassland intensification led to a decrease in measured supporting and regulating services, but increased forage productivity in temperate pastures and forage digestibility in subtropical pastures. Intensification decreased the net CO2 sink of subtropical pastures while it did not affect the sink capacity of temperate pastures; and it also increased environmental CH4 emissions from subtropical pastures and reduced CH4 uptake in temperate pastures. Intensification enhanced the global warming potential associated with C fluxes of pastures in both ecoregions. Our study demonstrates that comparisons of agroecosystems in contrasting ecoregions can reveal important drivers of ecosystem services and general or region-specific opportunities and solutions to maintaining agricultural production and reducing environmental footprints. Further LTAR network-scale comparisons of multiple ecosystem services across croplands and grazinglands intensively vs extensively managed are warranted to inform the sustainable intensification of agriculture within US and beyond. Our results highlight that achieving both food security and environmental stewardship will involve the conservation of less intensively managed pastures while adopting sustainable strategies in intensively managed pastures.

Trade‐offs and synergies between ecosystem productivity and stability in temperate grasslands

AbstractAimIt is crucial to monitor how the productivity of grasslands varies with its temporal stability for management of these ecosystems. However, identifying the direction of the productivity–stability relationship remains challenging because ecological stability has multiple components that can display neutral, positive or negative covariations. Furthermore, evidence suggests that the direction of the productivity–stability relationship depends on the biotic interactions and abiotic conditions that underlie ecosystem productivity and stability. We decipher the relationships between grassland productivity and two components of its stability in four habitat types with contrasting environments and flora.LocationFrance.Time period2000–2020.Major taxaGrassland plant species.MethodsWe used c. 20,000 vegetation plots spread across French permanent grasslands and remotely sensed vegetation indices to quantify grassland productivity and temporal stability. We decomposed stability into constancy (i.e., temporal invariability) and resistance (i.e., maximum deviation from average) and deciphered the direct and indirect effects of abiotic (namely growing season length and nitrogen input) and biotic (namely plant taxonomic diversity, trait diversity and community‐weighted mean traits) factors on productivity–stability relationships using structural equation models.ResultsWe found a positive relationship between productivity and constancy and a negative relationship between productivity and resistance in all habitats. Abiotic factors had stronger effects on productivity and stability compared with biotic factors. A longer growing season enhanced grassland productivity and constancy. Nitrogen input had positive and negative effects on grassland productivity and resistance, respectively. Trait values affected the constancy and resistance of grassland more than taxonomic and trait diversity, with effects varying from one habitat to another. Productivity was not related to any biotic factor.Main conclusionsOur findings reveal how vital it is to consider both the multiple components of stability and the interaction between environment and biodiversity to gain an understanding of the relationships between productivity and stability in real‐world ecosystems, which is a crucial step for sustainable grassland management.

Composted biosolids amendments for enhanced soil organic carbon and water storage in perennial pastures in Colorado

Land management of grasslands can play a significant role in climate change mitigation by influencing soil carbon (C) storage. Soil amendments, such as adding compost, have been shown to increase soil C storage while simultaneously increasing plant productivity and soil water holding capacity (WHC), factors that provide immediate benefits to ranchers. Research to date has mainly focused on temperate annual grasslands. However, little is known if irrigated perennial pasturelands in cold, arid climates respond similarly. This study’s objective was to determine the immediate effects of a 5 cm depth application of biosolids compost on plant productivity, soil moisture, and soil C storage. Research sites were established at four ranches in Gunnison, CO, a high-elevation, arid region. During the first year, there was a significant increase in total aboveground biomass (AGB) across three of the four sites (F3,32 = 62.3, p < 0.001), resulting in a difference in total AGB of 199.83 g·m−2 (95% CI 133.6 – 266.1 g·m−2) between the control and treatment, an average increase of 109% (SE ± 20%). There was a significant increase in soil moisture in the treatment plots relative to the controls at each site for most of the growing season (July-Oct). On average, soil organic matter (SOM) increased by 32% SE ± 10.5, with two sites demonstrating a significant increase. Soil C stocks increased across sites with biosolids, but this was only significant at one site (F1,32 = 7.05, p = 0.012), the most degraded of all four pasturelands. This study demonstrated that a single application of biosolids compost could elicit a significant increase in soil moisture throughout the growing season and increase plant biomass production. Biosolid applications can also increase SOC. However, this response's magnitude is site-specific and is associated with the degree of soil degradation, which might be related to land management history. Using biosolids compost on pasturelands seems to be a positive strategy to improve soil health and its associated co-benefits. Still, managers should consider the degree of degradation of their land when determining cost benefits.

The potential to increase grassland soil C stocks by extending reseeding intervals is dependent on soil texture and depth

Grasslands account for ∼30% of global terrestrial carbon (C), of which most is stored in soils and provide important ecosystem services including livestock and forage production. Reseeding of temporary grasslands on a 5-year cycle is a common management practice to rejuvenate sward productivity and reduce soil compaction, but is physically disruptive and may reduce soil organic carbon (SOC) stocks. However, research to date is limited, which impacts on the ability to optimise grassland management for climate change mitigation. To determine whether extending the time interval up to 20 years between grassland reseeding can increase stable SOC stocks, a soil survey was conducted across three UK grassland chrono-sequences comprising 24 fields on contrasting soil types. We found that grassland SOC stocks (39.8–114.8 Mg C ha−1) were higher than co-located fields in arable rotations (29.3–83.2 Mg C ha−1) and the relationship with grassland age followed a curvilinear relationship with rapid SOC stock accumulation in the year following reseeding (2.69–18.3 Mg C ha−1 yr−1) followed by progressively slower SOC accumulation up to 20 years. Contrary to expectation, all grasslands had similar soil bulk densities and sward composition questioning the need for traditional 5-year reseeding cycles. Fractionation of soils into stable mineral associated fractions revealed that coarse textured grassland topsoils (0–15 cm) were near-saturated in C irrespective of grassland age whilst loam soils reached saturation ∼10 years after reseeding. Fine-textured topsoils and subsoils (15–30 cm) of all textures were under saturated and thus appear to hold the most potential to accrue additional stable C. However, the lack of a relationship between C saturation deficit and grassland age in subsoils suggests that more innovative management to promote SOC redistribution to depth, such as a switch to diverse leys or full inversion tillage may be required to maximise subsoil SOC stocks. Taken together our findings suggest that extending the time between grassland reseeding could temporarily increase SOC stocks without compromising sward composition or soil structure. However, detailed monitoring of the trade-offs with grassland productivity are required. Fine textured soils and subsoils (15–30 cm) have the greatest potential to accrue additional stable C due to under saturation of fine mineral pools.

Environmental changes promoted vegetation growth and reduced water yield over the temperate semi-arid grassland of China during 1901–2016

As an important part of global semi-arid grassland, adequately understanding how eco-hydrological processes in the Temperate Semi-Arid Grassland of China (TSGC) respond to environmental change over a century-long time scale is of critical importance to environmental change adaptation and mitigation policy in the semi-arid region. We investigated the dynamics and driving forces of key eco-hydrological variables (leaf area index (LAI), gross primary production (GPP), evapotranspiration (ET), water yield (WY), and water use efficiency (WUE)) of 8 typical locations within the TSGC during the period 1901–2016, using a well-tested mechanistic eco-hydrological model, seamlessly integrating land-surface energy balance, hydrological and carbon cycle, vegetation dynamics, and soil biogeochemistry. Results show that dominated by the elevated CO2, the annual LAI, GPP, and WUE increased significantly during 1901–2016, indicating that the environmental conditions were conducive to vegetation growth. Warming conditions were a promoter of vegetation growth in sandy grassland but a suppressant in typical steppe due to water stress increase. For the same reason, ET of sandy grassland exhibited a significant increasing trend, in response to warming, while that of typical steppe had an insignificant decreasing trend, controlled by the precipitation decline. Warming and the vegetation growth acceleration due to the elevated CO2 negatively influenced WY, which showed a decreasing trend, especially in the sandy grassland, suggesting the reduction of available water resources. Overall, our results revealed that this region, especially sandy grassland, exhibited an “enhanced vegetation but decreased water yield” trend under environmental changes occurred in the past century.

Database of Japanese semi‐natural grassland flora

AbstractThe biodiversity of temperate grasslands can change considerably as a result of social and climate change. We have compiled information from published studies and created a database of Japanese semi‐natural grassland flora, which contains databases of flora of each grassland, grassland locations, and management methods. This database is useful as a basis for the analysis of changes in the flora of Japanese grasslands as well as for future monitoring. The detailed Metadata for this abstract published in the Data Article section of the journal are available in MetaCat in JaLTER at http://db.cger.nies.go.jp/JaLTER/metacat/metacat/ERDP-2023-01.1/jalter-en.

Identification of Constructive Species and Degraded Plant Species in the Temperate Typical Grassland of Inner Mongolia Based on Hyperspectral Data

In recent years, grassland degradation has become a global ecological problem. The identification of degraded grassland species is of great significance for monitoring grassland ecological environments and accelerating grassland ecological restoration. In this study, a ground spectral measurement experiment of typical grass species in the typical temperate grassland of Inner Mongolia was performed. An SVC XHR-1024i spectrometer was used to obtain field measurements of the spectra of grass species in the typical grassland areas of the study region from 6–29 July 2021. The parametric characteristics of the grass species’ spectral data were extracted and analyzed. Then, the spectral characteristic parameters + vegetation index, first-order derivative (FD) and continuum removal (CR) datasets were constructed by using principal component analysis (PCA). Finally, the RF, SVM, BP, CNN and the improved CNN model were established to identify Stipa grandis (SG), Cleistogenes squarrosa (CS), Caragana microphylla Lam. (CL), Leymus chinensis (LC), Artemisia frigida (AF), Allium ramosum L. (AL) and Artemisia capillaris Thunb. (AT). This study aims to determine a high-precision identification method based on the measured spectrum and to lay a foundation for related research. The obtained research results show that in the identification results based on ground-measured spectral data, the overall accuracy of the RF model and SVM model identification for different input datasets is low, but the identification accuracies of the SVM model for AF and AL are more than 85%. The recognition result of the CNN model is generally worse than that of the BP neural network model, but its recognition accuracy for AL is higher, while the recognition effect of the BP neural network model for CL is better. The overall accuracy and average accuracy of the improved CNN model are all the highest, and the recognition accuracy of AF and CL is stable above 98%, but the recognition accuracy of CS needs to be improved. The improved CNN model in this study shows a relatively significant grass species recognition performance and has certain recognition advantages. The identification of degraded grassland species can provide important scientific references for the realization of normal functions of grassland ecosystems, the maintenance of grassland biodiversity richness, and the management and planning of grassland production and life.

The recovery of plant community composition following passive restoration across spatial scales

Abstract Human impacts have led to dramatic biodiversity change which can be highly scale‐dependent across space and time. A primary means to manage these changes is via passive (here, the removal of disturbance) or active (management interventions) ecological restoration. The recovery of biodiversity, following the removal of disturbance, is often incomplete relative to some kind of reference target. The magnitude of recovery of ecological systems following disturbance depends on the landscape matrix and many contingent factors. Inferences about recovery after disturbance and biodiversity change depend on the temporal and spatial scales at which biodiversity is measured. We measured the recovery of biodiversity and species composition over 33 years in 17 temperate grasslands abandoned after agriculture at different points in time, collectively forming a chronosequence since abandonment from 1 to 80 years. We compare these abandoned sites with known agricultural land‐use histories to never‐disturbed sites as relative benchmarks. We specifically measured aspects of diversity at the local plot‐scale (α‐scale, 0.5 m2) and site‐scale (γ‐scale, 10 m2), as well as the within‐site heterogeneity (β‐diversity) and among‐site variation in species composition (turnover and nestedness). At our α‐scale, sites recovering after agricultural abandonment only had 70% of the plant species richness (and ~30% of the evenness), compared to never‐ploughed sites. Within‐site β‐diversity recovered following agricultural abandonment to around 90% after 80 years. This effect, however, was not enough to lead to recovery at our γ‐scale. Richness in recovering sites was ~65% of that in remnant never‐ploughed sites. The presence of species characteristic of the never‐disturbed sites increased in the recovering sites through time. Forb and legume cover declines in years since abandonment, relative to graminoid cover across sites. Synthesis. We found that, during the 80 years after agricultural abandonment, old fields did not recover to the level of biodiversity in remnant never‐ploughed sites at any scale. β‐diversity recovered more than α‐scale or γ‐scale. Plant species composition recovered, but not completely, over time, and some species groups increased their cover more than others. Patterns of ecological recovery in degraded ecosystems across space and long time‐scales can inform targeted active restoration interventions and perhaps, lead to better outcomes.

Forage nutritive value shows synergies with plant diversity in a wide range of semi-natural grassland habitats

This paper aims in assessing the relationship between grassland plant diversity and agronomic value, which represents a major challenge to reconcile nature conservation and agricultural use of semi-natural grassland habitats. The effects of plant diversity and functional traits were studied on forage nutritive value and early standing biomass in a wide set of semi-natural temperate grassland habitats. Plant communities were described by their species and functional diversity, community-weighted means (CWM) of plant functional traits, and the relative cover of main plant functional types (graminoids, forbs, and legumes). Species richness was found to be negatively associated with early standing biomass and average mineral content. Community evenness, for both species and plant functional types, was positively correlated with digestibility, crude protein content, and average mineral content but negatively with early standing biomass. Early standing biomass was found to increase with increasing graminoid cover and to decrease with increasing forb cover. Forage nutritive value improved with higher legume cover, higher specific leaf area CWM and lower leaf dry matter content CWM, while these functional community characteristics were not found to impact early standing biomass. Our results highlight that a better forage nutritive value can be obtained with a higher plant species evenness in permanent grassland habitats. Furthermore, in grasslands with an even distribution of plant functional types, forage nutritive value may be improved with no loss in early standing biomass.

No Signs of Long-term Greening Trend in Western Mongolian Grasslands

Trends for increased vegetation greenness based on satellite-derived data have been repeatedly published for the temperate grassland biome (including forest steppes) of eastern Inner Asia since 1982. Although this greening trend has been attenuated or partially reversed by drought in the early twenty-first century, linear increases in the Normalized Difference Vegetation Index (NDVI) or other parameters of vegetation greenness are nevertheless evident when the period since 1982 is regarded. However, the question arises whether these trends are part of a long-term trend driven by climate change, as simultaneously forests in the region show widespread drought-induced growth reductions and mortality outbreaks. Therefore, we hypothesized that the post-1982 greening trend was neither part of a long-term trend nor unprecedented. To test this hypothesis, we analyzed monthly maximum NDVI data from AVHRR time series and correlated these data with standardized tree-ring data of Larix sibirica from two regions of western Mongolia. We used linear regression to model the NDVI from tree-ring anomalies and to reconstruct the NDVI since 1940. These reconstructions show that the availability of satellite-based NDVI data coincidentally began during a dry period of low vegetation greenness in the early 1980s and was followed by a wet phase in the 1990s, producing the linear greening trend. No positive long-term trend in the reconstructed NDVI was observed from 1940 to 2010. This result rules out a recent climate change-driven greening trend for the grasslands and forest steppes of western Mongolia and calls into question its existence for all of eastern Inner Asia.

Variation in Soil Aggregate Stability Due to Land Use Changes from Alpine Grassland in a High-Altitude Watershed

Land use change affects soil aggregate composition and stability, which impacts soil structure and health. To reveal how land use change impacted soil aggregates of alpine grassland in a high-altitude watershed, soil samples from 161 sites including alpine grassland, cropland and abandoned land were selected to measure and analyze the distribution of aggregate fractions (macro-aggregates, micro-aggregates, silt+clay), soil aggregate stability (mean weight diameter, geometric mean diameter, fractal dimension, etc.) and related soil properties (soil organic carbon content, soil particle composition, etc.) in the Huangshui River watershed of the Qinghai–Tibet Plateau. The results showed: (1) As alpine grasslands were converted to croplands and croplands to abandoned lands, the proportion of macro-aggregates and the aggregate stability index showed a trend of first decreasing and then increasing (p &lt; 0.05), indicating that tillage and abandonment have significant influences on soil aggregate structure. (2) Compared with temperate grassland, alpine grassland had richer soil organic carbon, and a higher ratio of macro-aggregates and aggregate stability. (3) Soil organic carbon and sand content had distinct influences on the fractions and stability of aggregates during land use change. These results suggested that cultivation can substantially reduce the soil aggregate stability in alpine grassland, whereas abandonment can effectively improve soil aggregate structure.

Mammals of the Tandilia Mountain system, current species inhabiting Pampean highland grasslands

Neotropical temperate grasslands comprise the Pampas ecoregion in Argentina. This region is also the center of agricultural development in Argentina, which has led to a significant simplification and homogenization of the landscape. The Tandilia Mountains, located in the Southeast of the ecoregion, house one of the last remnants of the highland grassland that acts as a refuge for several native species, including both endemic and threatened species. This work aims to present an updated inventory of mammal species that inhabit the highland grassland remnants of the Tandilia Mountains. We used several sources of information to compile the list, including museum collections, citizen science projects (i.e., iNaturalist, EcoRegistros, and Argentinian Network for Monitoring Run Over Fauna), literature, and personal observations. We recorded 40 species of mammals, which include 32 native species and eight exotic species. The richest orders were Rodentia (42.5%), Chiroptera (17.5%), and Carnivora (12.2%). The native mammals found in the Tandilia Mountains represent 44% of the mammal diversity of the Pampas ecoregion, among which there are endemic species of the ecoregion, species whose populations are declining globally, and threatened species. Unfortunately, the presence of protected areas in the system is limited to a few small ones, which highlights the urgency of increasing the number and variety of protected areas. The information presented in this work contributes to the knowledge of biodiversity and the planning of conservation actions for the last remnants of highland grasslands.

Variability and drivers of grassland sensitivity to drought at different timescales using satellite image time series

Drought is expected to increase in frequency and severity with climate change, leading to more intense impacts on grasslands and their associated ecosystem services. Complementary to ground experiments, remote sensing technologies allow for the study of drought impacts with large spatio-temporal coverage in real-life-conditions. We aimed to quantify the variability of grassland sensitivity to drought using a long-term satellite image time series of 394 temperate permanent grassland plots to identify factors influencing these sensitivities. Accordingly, we assessed the slope of the linear relationship between satellite-based vegetation status, using the standardized anomalies of the vegetation indices (VIs), and drought severity, using a modified version of the Standardized Precipitation Evapotranspiration Index (SPEI), from 1985 to 2019. The process was repeated for 24 VIs and five SPEI timescales. We then conducted a linear model selection procedure, using the grassland sensitivity derived from the most responsive VIs (i.e., VIs for which anomalies indicated a tighter linear relationship with the modified SPEI), to identify which grassland properties influenced sensitivity to drought. A total of 29 properties, grouped into pedoclimate, agricultural management, and vegetation diversity factors, were derived from ground measurements. Overall, we demonstrated that the influence of predictors on grassland sensitivity to drought varied across the drought integration timescales. Our results highlighted the significant mitigating effect of soil water holding capacity on sensitivity to drought for short timescales of fewer than 30 days. The date of first herbage use by farmers was positively related to grassland sensitivity to drought across all timescales. We also demonstrated that higher vegetation diversity significantly reduced sensitivity to drought. However, for the long timescales of drought integration, such influence was mainly redundant with management (i.e., shared partition of variance) suggesting complex cascading effects between agricultural practices and plant community structure that still need to be addressed comprehensively in future studies.

Drought effects on root and shoot traits and their decomposability

Abstract Drought can induce phenotypic plasticity in a range of plant root and shoot traits. These traits have been shown to explain differences in root and shoot litter decomposability between species. However, it is unknown how drought‐induced plasticity of root and shoot traits alters their decomposability. To investigate this issue across a range of species, we grew a grass Lolium perenne, a forb Plantago lanceolata and a legume Trifolium repens common to European temperate grasslands and subjected them to a 5‐week moderate drought treatment. We compared morphological and chemical root and shoot traits of the droughted plants to well‐watered controls. We then conducted a decomposition assay of the senesced root and shoot material over 16 weeks, with mass loss measurements at five timepoints. Drought had significant and sometimes strong effects on morphological and chemical root and shoot traits of all three species, sometimes similar to differences between species and generally in line with a shift to a more resource‐conservative strategy. Drought also increased the labile litter fraction in roots of Lolium perenne, which was associated with a substantial increase in non‐structural carbohydrates. Drought decreased the labile litter fraction in shoots of Plantago lanceolata, but this could not be explained by the traits we measured. Drought effects on litter decomposability were weaker than on plant traits. Our results suggest that plant trait‐mediated effects of drought on litter decomposability can either increase or decrease vegetation feedbacks to climate change. They also show that drought‐induced plasticity in root and shoot traits does not automatically translate into equivalent changes in litter decomposability. Read the free Plain Language Summary for this article on the Journal blog.