Search Results (19)

Grassland-based livestock systems across Mexico’s arid and semi-arid belt are increasingly exposed to drought, degrading forage reliability, and soil function. This review synthesizes evidence on native C4 grasses and forage shrubs as complementary building blocks of drought-resilient swards. We searched Web of Science, Scopus, CAB Abstracts and key grey sources (USDA/NRCS Plant Guides, USFS FEIS, Tropical Forages, SNICS) for 1990–2025 studies in English/Spanish. Dominant native grasses (Bouteloua spp., Hilaria belangeri, Digitaria californica, Trichloris crinita, Sporobolus airoides, Panicum hallii) provide high warm-season digestibility and structural cover via C4 physiology, basal/intercalary meristems, and deep/fibrous roots. Forage shrubs (Atriplex canescens, Desmanthus bicornutus, Leucaena leucocephala, Flourensia cernua, Prosopis spp.) bridge the dry-season protein/energy gap and create “resource islands” that enhance infiltration, provided anti-nutritional risks (mimosine/DHP, tannins, salts/oxalates, terpenoids) are managed by dose and diet mixing. We integrate these findings into a Resistance–Recovery–Persistence framework and translate them into operations: (i) site-matching rules for species/layouts, (ii) PLS (pure live seed)-based seed specifications and establishment protocols, (iii) grazing TIDD (timing–intensity–distribution–duration) with a practical monitoring dashboard (CP targets, stubble/cover thresholds, NDVI/SPEI triggers). Remaining bottlenecks are seed quality/availability and uneven extension; policy alignment on PLS procurement and regional seed increase can accelerate adoption. Mixed native grass–shrub systems are a viable, scalable pathway to strengthening drought resilience in Mexican rangelands. Full article

The advancement of hyperspectral remote sensing technology has enhanced the ability to assess and characterize land cover in complex ecosystems. In this study, a linear spectral unmixing algorithm was applied to NEON hyperspectral imagery in 2018 and 2022 to quantify the fractional abundance of dominant land cover classes, namely herbaceous vegetation, mixed forbs, and bare soil, across the Marvin Klemme Experimental Rangeland in Oklahoma. UAV imagery acquired during the 2023 field campaign provided high resolution reference data for model training. The LSU results revealed a decline in herbaceous cover from 16.02 ha to 11.56 ha and an expansion of bare soil from 3.37 ha to 6.39 ha, while mixed forb cover remained relatively stable (12.38 ha to 13.82 ha). Accuracy assessment using the UAV-derived validation points yielded overall accuracy of 84% and 60% at fractional thresholds of 50% and 75%, respectively. Although statistical tests indicated no significant change in mean fractional abundance (p > 0.05), slope-based trend maps captured localized vegetation loss and regrowth patterns. These findings demonstrate the effectiveness of integrating LSU with UAV data for detecting subtle yet ecologically meaningful shifts in semi-arid grassland composition. Full article

Mixed legume/grass grasslands are the most significant type of artificial grassland in rain-fed semi-arid regions. Understanding the contributions of legumes and grasses to grassland productivity, as well as the nitrogen-sharing mechanisms between them, is crucial to maintaining the sustainability, stability, and high yield of mixed grasslands. In this study, four commonly used cultivated species were selected: smooth bromegrass (Bromus inermis Leyss.), orchardgrass (Dactylis glomerata L.), sainfoin (Onobrychis viciifolia Scop.), and red clover (Trifolium pratense L.). Combinations of two and three species of legumes and grasses were established, with monoculture serving as the control. The results revealed that in all the monocultures and mixed grasslands comprising two or three species, the average dry matter yield (DMY) of mowed grasslands in 2017 was significantly higher than in 2018, while the average DMY of grazed summer regrowth in 2018 surpassed that of 2016 and 2017. Over the period from 2016 to 2018, smooth bromegrass and sainfoin gradually dominated the mixed grasslands, while orchardgrass and red clover exhibited a declining abundance. Over time, the ratio and amount of nitrogen (N) fixation in legumes significantly increased in both the monoculture and mixed grasslands. Similarly, the amount of nitrogen (N) received by grasses also increased significantly in mixed grasslands. However, the proportion of nitrogen fixed by legumes remained below 10% in 2016, 20% in 2017, and 30% in 2018. In contrast, nitrogen transfer from legumes to smooth bromegrass was less than 10%, while in orchardgrass, it was even lower, at less than 2%. The interannual variability in dry matter yield (DMY) and nitrogen contribution in the mixed grasslands of rain-fed semi-arid areas is primarily influenced by forage adaptability and average annual precipitation. Increasing the proportion of grazed forage relative to hay in annual forage consumption should be considered, as more extensive grazing can reduce damage from field rodents and provide higher forage quality at lower costs and energy consumption. To maintain grassland productivity, targeted grazing should be carefully planned and implemented. Full article

Identification of paleoclimate oscillation from various climate proxies across different regions is important for the mechanistic research of paleoclimate. Phytoliths from the lacustrine sediment of central NE China were extracted for paleoclimate reconstruction and abrupt event recognition. The combined phytolith assemblages; indices of Iw, Iph, D/P, Pi/P, and T/P; and the 66.4% PCA information with 95% confidence ellipse showed six global synchronously paleo-stages in the past 25,000 years: mixed coniferous broadleaf forest in a semi-humid cool climate (25,165–22,180 cal aB.P.), cold and arid steppe (22,180–18,080 cal aB.P.), semi-humid and semi-arid steppe (18,080–11,380); semi-humid cool grassland (11,380–7790 cal aB.P.), humid warm forest steppe (7790–4300 cal aB.P.), and semi-arid and cool meadow steppe (4300 cal aB.P. to the present). The global abrupt events of the 4.2-kiloyear event, 8.2-kiloyear event, Younger Dryas (YD), Heinrich1 (H1), and Heinrich2 (H2) were also captured by phytolith indices. The regional character of the reduction in humidity of the YD might have been affected by the combined influence of the Okhotsk High and the surrounding mountains. These findings not only strengthen phytolith palaeoresearch but also provide basic information for the mechanistic research of palaeoclimate in the edge area of Northeast Asia and promote global climate change research. Full article

Nitrogen (N) fertilization is an effective practice for restoring degraded grasslands, which might strongly depend on the rooting system and resource competition of individual plant species. The purpose of this study is to explore a method to distinguish the response of various plant root architectures to the resource availability in a mixed ecosystem in situ. Field experiments were conducted using isotope techniques in conjunction with a specialized experimental design at a semiarid grassland location featuring heavily grazed (HG) and moderately grazed (MG) grassland sites with different dominant species. The same amounts of water and ¹⁵N-labelled fertilizer were uniformly supplied by a tube fertigation system at soil depths of 0, 15 and 45 cm. At both the HG and MG sites, there was a significant increase in aboveground net primary production (ANPP), water use efficiency (WUE) and ¹⁵N use efficiency (¹⁵NUE) at the community level with increasing depths of fertigation. The ANPP and plant N uptake exhibited higher values at the HG site compared to those at the MG site, while ¹⁵NUE and ¹⁵N abundance were significantly lower at the HG site. The annual species Salsola collina Pall. exhibited the highest aboveground biomass (AGB) and ¹⁵N abundance compared to all other species. Furthermore, the ¹⁵N enrichment of S. collina increased with greater depths of ¹⁵N-labelled fertilization, indicating that S. collina might develop a more extensive root system in response to water and N addition in the degraded grassland. Our study highlights that using isotope methods could indirectly distinguish root distribution and resource acquisition. In the recovery of degraded grassland by N fertilizer, we should not only consider the aboveground biomass but also pay special attention to the resource competition of individual plant species due to the possible discrepancy in rooting systems. Full article

The spatial distribution of soil moisture is a critical determinant for the success of vegetation restoration initiatives in semi-arid and arid regions. The Qilian Mountains, situated within a semi-arid zone in China, have been subject to significant water-induced soil erosion, which has led to extensive restoration activities, predominantly utilizing the species P. crassifolia. However, the interconnections between soil moisture and various land cover types within this region remain unclear, presenting challenges to effective woodland rehabilitation. This study examines the surface soil moisture dynamics in afforested areas with varying ages of plantation to determine the influence of tree planting on the moisture content of the upper soil layer. It investigates the characteristics and temporal patterns of surface soil moisture as the age of the plantation increases. The findings indicate that: (1) soil moisture levels follow a descending sequence from natural forest, through shrubland and grassland, to planted forest and mixed forest, with statistically significant differences observed between natural and mixed forests (p < 0.05); (2) young afforested areas (less than 50 years old) have lower soil moisture levels compared to natural forests, shrublands, or grasslands, and the ecohydrological impacts of afforestation become apparent with a temporal delay; and (3) the analysis using Generalized Additive Mixed Models (GAMM) and the application of Kriging interpolation to determine the spatial distribution of soil moisture reveals that in semi-arid and arid regions, several factors have a pronounced a non-linear relationship with the moisture content of the surface soil. These factors include the duration of afforestation, the position on the lower slope, the presence of shade on the slope, and the scale at which the study is conducted. Therefore, a comprehensive understanding of the dynamics of soil water content is essential to prevent the potential failure of artificially established forests due to inadequate soil moisture in their later stages. Full article

Biodiversity is under threat due to human-induced changes in land use. While various aspects of biodiversity are increasingly studied in response to these changes, there is limited understanding of their effects on the structure and composition of bird communities in dryland regions. We examined the impacts of land use change on birds in the semi-arid area of the Longxi Loess Plateau by considering taxonomic diversity, functional diversity, and phylogenetic diversity. We analyzed both the α- and β-diversity of avian communities across different dimensions of diversity and calculated functional and phylogenetic structures using the net relatedness index. Our findings revealed that species richness was highest in farmland and abandoned farmland, while artificial mixed forests exhibited the highest number of unique species. Functional and phylogenetic α-diversity was greater in farmland and abandoned farmland when compared to the other four land use types. Moreover, the taxonomic diversity in artificial mixed forests, artificial Caragana korshinskii forests, and artificial Platycladus orientalis forests surpassed that in typical grasslands, but no differences were observed in functional and phylogenetic diversity. Regarding β-diversity, turnover patterns dominated multidimensional dissimilarity, with taxonomic turnover and total dissimilarity lower than their functional counterparts but higher than phylogenetic counterparts. Based on the present findings, we emphasize the long-term cessation of ongoing silvicultural initiatives to safeguard bird diversity in the semi-arid region of the Longxi Loess Plateau. This is crucial for narrowly distributed species such as Alectoris magna, as they face heightened vulnerability to losses. Full article

Water-conservation enhancement is a crucial objective of regional ecological restoration projects in arid and semiarid areas, and it is significantly influenced by land use/cover change (LUCC). The Grain for Green Project (GFGP) is a common strategy for ecological restoration. However, insufficient attention has been paid to the impact of reforestation patterns and the underlying surface characteristics on the effectiveness of GFGP in enhancing water conservation. In this study, a Soil and Water Assessment Tool (SWAT) scenario-based simulation was conducted to assess changes in water-conservation depth (WCD) in the Zhangjiakou section of the Guanting Reservoir basin. Redundancy analysis (RDA) and a mixed linear model were employed to determine the effects of different reforestation patterns and their underlying slope gradient and soil-type characteristics on WCD variation. The results showed that there were differences in the effect characteristics of reforestation patterns and different vegetation types on WCD changes; the effectiveness of increased water conservation is associated with the adaptation of reforestation plants to underlying characteristics. Returning farmland to evergreen forests was the most effective approach, leading to a relative increase in WCD that was 2.6 times greater than the relative increase in total WCD. WCD decreased with the slope gradient, with WCD decreasing by 0.2 mm for every 1° increase in slope. Converting grassland to evergreen forests on slopes greater than 16.19° and converting deciduous forests to grassland on slopes less than 16.19° would further increase WCD, promoting the synergistic development of ecosystem services. This study provides insights into the development of more efficient reforestation strategies to enhance water conservation in a complex terrain area. Full article

The effect of global warming and desertification on bird populations of semi-arid North African ecosystems has been little studied, although ecosystems in those areas are suffering dramatic changes. Dupont’s lark is one of the most endangered passerines in Europe, but it is also considered scarce in North Africa, where its range and numbers are only well known for Morocco. We analyzed the current distribution and population size of Dupont’s lark in Tunisia and compared the current figures with older data. To assess the presence of the species in the patches of adequate habitat that we found, we elicited territorial calls by broadcasting the males’ territorial songs during early breeding season (N = 123, ≈40 h). Fieldwork (45 persons/day) and analysis of satellite images were combined to determine the current minimal extent of occurrence and area of occupancy, following IUCN definitions. In the only habitat where we found the species (well-preserved pure or mixed alfa patches in the Feriana-Kasserine region), the extent of occurrence in and effective area of occupancy were small (56.3 and 33.2 km², respectively), particularly when compared with previous estimates (presence of the species in adequate habitat over ca. 89,000 km²). The species has not been detected at all in a large area in the southern part of its potential range, where additional surveys are urgently needed to locate possible remnant small and isolated populations that could persist, as suggested by two recent records of the species there. The breeding population of Dupont’s lark in Tunisia is estimated to be fewer than 600 song birds (335–577). The drastic reduction of range and numbers of this species must have been caused by the disappearance or degradation of alfa grasslands due to agricultural development, overgrazing, and increased aridity. Full article

Nitrogen is a key factor influencing ecosystem structure and function in reforestation, but knowledge of ecosystem nitrogen accumulation through reforestation with mixed species is limited. Especially in the dry-hot valley of the Jinsha River, no studies cover total ecosystem nitrogen accumulation in mature plantations and its allocation for difficulty in collecting tree roots and deep soil from dry red soil. In this study, nitrogen accumulation of seven mixed plantations in the dry-hot valley in the Jinsha River was studied after thirty years of reforestation with an analogous sites method. The results were as follows: (1) Soil nitrogen stocks decreased with depth in the soil profile. Deep soil nitrogen storage (20–80 cm) was significantly correlated with stand age (R² = 0.752, p = 0.000; n = 7), accounting for 56–63% of total soil nitrogen storage and 43–47% of soil nitrogen accumulation in the dry-hot valley. (2) Total biomass nitrogen stock of the 30-year-old plantation was 1.22 t ha⁻¹, 61 times that of degraded wasteland and 7.6 times that of natural recovery shrub grassland, and it recovered to the reference level of natural forest following 30 years of reforestation. (3) Total ecosystem nitrogen stock in the 30-year-old plantation was 12.72 t ha⁻¹, 1.4 times the reference wasteland and 1.19 times the natural recovery shrub grassland. The contribution of soil nitrogen to ecosystem nitrogen storage and accumulation was 90% and 67%, respectively. Litter nitrogen accounted for 1.6% ecosystem nitrogen storage. It indicated that reforestation with mixed plantation of Leucaena leucocephala and other species greatly facilitated more ecosystem nitrogen accumulation, especially soil nitrogen (including deep compartment). Secondary biomass nitrogen, especially litter, could not be overlooked. This study filled the gap of ecosystem nitrogen storage and distribution during reforestation in the dry-hot valley. Mixed plantation with legume species such as L. leucocephala and other species and an important role of secondary biomass, especially litter in nitrogen accumulation, provided a reference for the strategy formulation of reforestation and forest nitrogen management in the dry-hot valley and other semi-arid or arid regions. Full article

Soil moisture is the key factor controlling plant growth in semiarid grasslands. Here, we sought to evaluate the effects of soil moisture decreasing at different growth stages on biomass accumulation, water use efficiency, and plant-plant interaction of a C₃ leguminous subshrub Lespedeza davurica (L) and a C₄ perennial grass Bothriochloa ischaemum (B) when sown singly and as a mix in five different ratios in a pot experiment. Results showed that soil water decrease significantly reduced total biomass production of the mixtures by 3.7–53.8% compared with well-watered conditions, and plants at the heading and flowering periods were more vulnerable to soil water decline than those at the late stage. The relative yield total (RYT) of the mixtures was mostly greater than those sown singly. Soil water decreasing increased root/shoot ratio and water use efficiency (WUE) of the mixtures, and such effects were mediated by mixture ratio and/or growth stage. In the mixtures, a strong intraspecific competition was observed in B. ischaemum, whereas interspecific competition in L. davurica. The highest overall biomass (86.47 g pot⁻¹) and WUE (6.33 g kg⁻¹) were observed when the mixture ratio was B:L = 10:2 regardless of soil moisture, and thus could be considered an optimal mixture ratio for establishing restored grassland using the two species. Our results suggest that sown seed mixtures of the two species with an appropriate ratio could sustain a relatively high total biomass production and improve WUE under soil water decreasing conditions in the semiarid Loess Plateau. Full article

Vegetation restoration is considered a potentially useful strategy for controlling soil erosion and improving soil organic carbon (SOC) in arid and semiarid ecosystems. However, there is still debate regarding which vegetation restoration type is the best choice. In this study, four vegetation restoration types (i.e., grasslands, shrubs, forests and mixed forests) converted from sloping farmlands were selected to explore the SOC variation among the four types and to investigate which soil factors had the greatest effect on SOC. The results showed while the magnitude of effect differed between vegetation restoration type, all studied systems significantly increased SOC and labile organic carbon contents (p < 0.01), soil nutrients such as total nitrogen (TN) (p < 0.01), available nitrogen (AN) (p < 0.01), total phosphorus (TP) (p < 0.05) and available phosphorus (AP) (p < 0.05), soil enzyme activities such as phosphatase (p < 0.01), soil microbial biomass carbon (MBC) (p < 0.05), and basal respiration (BR) (p < 0.05), but had significant negative correlationswith polyphenol oxidase (p < 0.05). However, the effects of vegetation restoration of farmland converted to natural grasslands, shrubs, forests and mixed forests varied. Among the types studied, the mixed forests had the largest overall positive effects on SOC overall, followed by the natural grasslands. Soil nutrients such as N and P and soil microbial activities were the main factors that affected SOC after vegetation restoration. Mixed forests such as Robinia pseudoacacia and Caragana korshinskii are the best choice for farmland conversion on the central of the Loess Plateau. Full article

The ability to quantify green vegetation across space and over time is useful for studying grassland health and function and improving our understanding of the impact of land use and climate change on grasslands. Directly measuring the fraction of green vegetation cover is labor-intensive and thus only practical on relatively smaller experimental sites. Remote sensing vegetation indices, as a commonly-used method for large-area vegetation mapping, were found to produce inconsistent accuracies when mapping green vegetation in semi-arid grasslands, largely due to mixed pixels including both photosynthetic and non-photosynthetic material. The spectral mixture approach has the potential to map the fraction of green vegetation cover in a heterogeneous landscape, thanks to its ability to decompose a spectral signal from a mixed pixel into a set of fractional abundances. In this study, a time series of fractional green vegetation cover (FGVC) from 1999 to 2014 is estimated using the spectral mixture approach for a semi-arid mixed grassland, which represents a typical threatened, species-rich habitat in Central Canada. The shape of pixel clouds in each of the Landsat images is used to identify three major image endmembers (green vegetation, bare soil/litter, and water/shadow) for automated image spectral unmixing. The FGVC derived through the spectral mixture approach correlates highly with field observations (R² = 0.86). Change in the FGVC over the study period was also mapped, and green vegetation in badlands and uplands is found to experience a slight increase, while vegetation in riparian zone shows a decrease. Only a small portion of the study area is undergoing significant changes, which is likely attributable to climate variability, bison reintroduction, and wildfire. The results of this study suggest that the automated spectral unmixing approach is promising, and the time series of medium-resolution images is capable of identifying changes in green vegetation cover in semi-arid grasslands. Further research should investigate driving forces for areas undergoing significant changes. Full article

Alpine grasslands are a common feature on the extensive (2.6 million km²) Qinghai–Tibet plateau in western and southwestern China. These grasslands are characterized by their ability to thrive at high altitudes and in areas with short growing seasons and low humidity. Alpine steppe and alpine meadow are the principal plant Formations supporting a rich species mix of grass and forb species, many of them endemic. Alpine grasslands are the mainstay of pastoralism where yaks and hardy Tibetan sheep and Bactrian camels are the favored livestock in the cold arid region. It is not only their importance to local semi nomadic herders, but their role as headwaters of nine major rivers that provide water to more than one billion people in China and in neighboring countries in south and south-east Asia and beyond. Grasslands in this region were heavily utilized in recent decades and are facing accelerated land degradation. Government and herder responses, although quite different, are being implemented as climate change and the transition to the market economy proceeds apace. Problems and prospects for alpine grasslands and the management regimes being imposed (including sedentarization, resettlement and global warming are briefly discussed. Full article

A 5-year study evaluated the change in the quantity of soil total C (STC), soil organic C (SOC), and soil inorganic C (SIC) stored in the surface 60 cm of the soil profile on two adjacent blocks of land with a long-term history of cropping (CH) or undisturbed grassland (NH) on similar soil types between 1999 and 2004. The NH area was tilled and a grass-legume species mix was seeded into plots on both the NH and the CH areas. Selected plots of restored grass were established so they could be grazed (GG) by livestock while other plots were left ungrazed (UG). Original undisturbed (and ungrazed) grassland plots within the NH area were used as a control treatment. Initially, STC and SOC in CH were lower than NH when compared under the semi-arid environmental conditions found in southwestern North Dakota. Over the study period, the undisturbed grass control plots had increases in STC and SOC levels in the soil profile of 3.90 kg·m⁻² and 3.34 kg·m⁻², respectively. Restored grass on the NH area with grazing showed increases in STC and SOC values of 2.11 and 1.26 kg·m⁻², respectively, while without grazing, profile STC and SOC had values of 3.80 and 3.28 kg·m⁻², respectively. Restored grass on the CH area showed increases in profile STC and SOC values of 0.55 and 1.96 kg·m⁻², respectively, for the grazed plots and 0.78 and 2.11 kg·m⁻², respectively, when left ungrazed. Soil inorganic C, though present in the soils, did not significantly change during the study. The lower C accumulation in the CH plots may be due to a lag time in the establishment of mycorrhizal associations with the seeded species, the inoculums of which were already present in the NH soils. Changes in STC were likely due to changes in water relationships in the soil profile where management changes affected water infiltration and its movement causing leaching of SIC below the 60 cm depth evaluated. Soils under undisturbed grassland continue to accumulate carbon while soils of the disturbed grassland or cropped prior to re-establishing grass showed losses that occurred due to either accumulating C at a lower rate or perhaps to C loss during the initial establishment period (1–2 years). Full article