• Energy Research

Significance Accurate prediction of community responses to global change drivers (GCDs) is critical given the effects of biodiversity on ecosystem services. There is consensus that human activities are driving species extinctions at the global scale, but debate remains over whether GCDs are systematically altering local communities worldwide. Across 105 experiments that included over 400 experimental manipulations, we found evidence for a lagged response of herbaceous plant communities to GCDs caused by shifts in the identities and relative abundances of species, often without a corresponding difference in species richness. These results provide evidence that community responses are pervasive across a wide variety of GCDs on long-term temporal scales and that these responses increase in strength when multiple GCDs are simultaneously imposed.

AbstractLoss of plant diversity with increased anthropogenic nitrogen (N) deposition in grasslands has occurred globally. In most cases, competitive exclusion driven by preemption of light or space is invoked as a key mechanism. Here, we provide evidence from a 9‐yr N‐addition experiment for an alternative mechanism: differential sensitivity of forbs and grasses to increased soil manganese (Mn) levels. In Inner Mongolia steppes, increasing the N supply shifted plant community composition from grass–forb codominance (primarily Stipa krylovii and Artemisia frigida, respectively) to exclusive dominance by grass, with associated declines in overall species richness. Reduced abundance of forbs was linked to soil acidification that increased mobilization of soil Mn, with a 10‐fold greater accumulation of Mn in forbs than in grasses. The enhanced accumulation of Mn in forbs was correlated with reduced photosynthetic rates and growth, and is consistent with the loss of forb species. Differential accumulation of Mn between forbs and grasses can be linked to fundamental differences between dicots and monocots in the biochemical pathways regulating metal transport. These findings provide a mechanistic explanation for N‐induced species loss in temperate grasslands by linking metal mobilization in soil to differential metal acquisition and impacts on key functional groups in these ecosystems.

La sécheresse extrême a un impact considérable sur la fonction et les processus de l'écosystème. Cependant, une compréhension globale de la façon dont la sécheresse extrême affecte la biomasse racinaire à l'échelle régionale reste insaisissable. Ici, nous avons étudié les effets sur six prairies avec un traitement de sécheresse extrême répliqué sur un gradient de précipitations en Mongolie intérieure, en Chine. Nous avons constaté que la biomasse racinaire et la productivité primaire nette souterraine (BNPP) étaient significativement corrélées positivement avec les précipitations à l'échelle réginale. La sécheresse extrême a diminué la pente de cette corrélation de 0 à 10 cm et a augmenté de 10 à 20 cm. La biomasse racinaire et le BNPP ont augmenté par la sécheresse extrême dans les quatre sites relativement arides et diminué dans les deux sites relativement mésiques de 0 à 10 cm, et le schéma inverse a été montré de 10 à 20 cm. Ces changements ont été entraînés par la réponse de l'humidité du sol. Nos résultats suggèrent que l'inclusion de réponses verticales de la productivité primaire souterraine à la sécheresse extrême devrait améliorer les prédictions des modèles de racines végétales au changement climatique futur. La sequía extrema afecta la función y los procesos del ecosistema de manera dramática. Sin embargo, una comprensión integral de cómo la sequía extrema afecta la biomasa de la raíz a escalas regionales sigue siendo difícil de alcanzar. Aquí, investigamos los efectos en seis pastizales con tratamiento de sequía extrema replicado en un gradiente de precipitación en Mongolia Interior, China. Encontramos que la biomasa de la raíz y la productividad primaria neta subterránea (BNPP) se correlacionaron significativamente de manera positiva con la precipitación a escala reginal. La sequía extrema disminuyó la pendiente de esta correlación en 0-10 cm y aumentó en 10-20 cm. La biomasa de la raíz y la BNPP aumentaron por la sequía extrema en los cuatro sitios relativamente áridos y disminuyeron en los dos sitios relativamente mesicos en 0-10 cm, y el patrón inverso mostrado en 10-20 cm. Estos cambios fueron impulsados por la respuesta de la humedad del suelo. Nuestros hallazgos sugieren que la inclusión de respuestas verticales de la productividad primaria subterránea a la sequía extrema debería mejorar las predicciones de los modelos de las raíces de las plantas al cambio climático futuro. Extreme drought impacts ecosystem function and processes dramatically.However, a comprehensive understanding of how extreme drought affects root biomass at regional scales remains elusive.Here, we investigated the effects across six grasslands with extreme drought treatment replicated across a precipitation gradient in Inner Mongolia, China.We found the root biomass and belowground net primary productivity (BNPP) were significantly positively correlated with precipitation at the reginal scale.Extreme drought decreased the slope of this correlation in 0-10 cm and increased in 10-20 cm.Root biomass and BNPP increased by extreme drought in the four relatively arid sites and decreased in the two relatively mesic sites in 0-10 cm, and the reverse pattern showed in 10-20 cm.These shifts were driven by the response of soil moisture.Our findings suggest that including vertical responses of belowground primary productivity to extreme drought should improve models predictions of plant roots to future climate change. يؤثر الجفاف الشديد على وظيفة النظام البيئي وعملياته بشكل كبير. ومع ذلك، فإن الفهم الشامل لكيفية تأثير الجفاف الشديد على الكتلة الحيوية للجذور على النطاقات الإقليمية لا يزال بعيد المنال. هنا، قمنا بالتحقيق في الآثار عبر ستة مراعي مع معالجة الجفاف الشديد التي تتكرر عبر تدرج هطول الأمطار في منغوليا الداخلية، الصين. وجدنا أن الكتلة الحيوية للجذور والإنتاجية الأولية الصافية تحت الأرض (BNPP) كانت مرتبطة بشكل إيجابي بشكل كبير مع هطول الأمطار على نطاق ريجنال. أدى الجفاف الشديد إلى انخفاض ميل هذا الارتباط في 0-10 سم وزاد في 10-20 سم. زادت الكتلة الحيوية للجذور و BNP بسبب الجفاف الشديد في المواقع الأربعة القاحلة نسبيًا وانخفضت في الموقعين المتوسطين نسبيًا في 0-10 سم، وأظهر النمط العكسي في 10-20 سم. كانت هذه التحولات مدفوعة باستجابة رطوبة التربة. تشير نتائجنا إلى أن بما في ذلك الاستجابات الرأسية للإنتاجية الأولية تحت الأرض للجفاف الشديد يجب أن تحسن نماذج جذور النباتات لتغير المناخ في المستقبل.

AbstractAtmospheric nitrogen (N) deposition is composed of both inorganic nitrogen (IN) and organic nitrogen (ON), and these sources of N may exhibit different impacts on ecosystems. However, our understanding of the impacts of N deposition is largely based on experimental gradients of INs or more rarely ONs. Thus, the effects of N deposition on ecosystem productivity and biodiversity may be biased. We explored the differential impacts of N addition with different IN:ON ratios (0:10, 3:7, 5:5, 7:3, and 10:0) on aboveground net primary productivity (ANPP) of plant community and plant diversity in a typical temperate grassland with a long‐term N addition experiment. Soil pH, litter biomass, soil IN concentration, and light penetration were measured to examine the potential mechanisms underlying species loss with N addition. Our results showed that N addition significantly increased plant community ANPP by 68.33%–105.50% and reduced species richness by 16.20%–37.99%. The IN:ON ratios showed no significant effects on plant community ANPP. However, IN‐induced species richness loss was about 2.34 times of ON‐induced richness loss. Soil pH was positively related to species richness, and they exhibited very similar response patterns to IN:ON ratios. It implies that soil acidification accounts for the different magnitudes of species loss with IN and ON additions. Overall, our study suggests that it might be reasonable to evaluate the effects of N deposition on plant community ANPP with either IN or ON addition. However, the evaluation of N deposition on biodiversity might be overestimated if only IN is added or underestimated if only ON is added.

AbstractEcosystem structure, functioning, and stability have been a focus of ecological and environmental sciences during the past two decades. The mechanisms underlying their relationship, however, are not well understood. Based on comprehensive studies in Inner Mongolia grassland, here we show that species-level stoichiometric homeostasis was consistently positively correlated with dominance and stability on both 2-year and 27-year temporal scales and across a 1200-km spatial transect. At the community level, stoichiometric homeostasis was also positively correlated with ecosystem function and stability in most cases. Thus, homeostatic species tend to have high and stable biomass; and ecosystems dominated by more homeostatic species have higher productivity and greater stability. By modulating organism responses to key environmental drivers, stoichiometric homeostasis appears to be a major mechanism responsible for the structure, functioning, and stability of grassland ecosystems.

Shrub encroachment induced by global change and human disturbance strongly affects ecosystem structure and function. In this study, we explore the degree to which invading leguminous shrubs affected neighboring grasses, including via the transfer of fixed nitrogen (N). We measured N concentrations and natural abundance (15)N of shoot tissues from three dominant grasses from different plant functional groups across seven distances along a local transect (up to 500 cm) to the leguminous shrub, Caragana microphylla. C. microphylla did transfer fixed N to neighboring grasses, but the amount and distance of N transferred were strongly species-specific. Shoot N concentrations decreased significantly with distance from C. microphylla, for a rhizomatous grass, Leymus chinensis, and a bunchgrass, Achnatherum sibiricum. However, N concentrations of another bunchgrass, Stipa grandis, were higher only directly underneath the shrub canopy. Shoot δ(15)N values of L. chinensis were enriched up to 500 cm from the shrub, but for S. grandis were enriched only below the shrub canopy. In contrast, δ(15)N of A. sibiricum did not change along the 500-cm transect. Our results indicated the rhizomatous grass transferred fixed N over long distances while bunchgrasses did not. The presence of C. microphylla increased the shoot biomass of L. chinensis but decreased that of S. grandis and A. sibiricum. These findings highlight the potential role of nutrient-acquisition strategies of neighboring grasses in moderating the interspecific variation of fixed N transfer from the leguminous shrub. Overall, leguminous shrubs have either positive or negative effects on the neighboring grasses and dramatically affect plant community composition and structure.

Abstract Global climate change is causing notable shifts in the environmental suitability of the main regions involved in potato cultivation and has, thus, changed the production potential of potatoes. These shifts can be mapped at fine scales to better understand climate change within areas of potato cultivation and to find infrastructural- and breeding-based solutions. As a case study, we have identified and mapped the structural and spatial shifts that occurred in areas suitable for potato cultivation in Jilin Province, China. We identified a discontinuity in climate change trends between 1961 and 2018 based on data for Jilin Province, and analyzed the averages and linear trends for six important climatic parameters. We used the averages of these climatic parameters to establish climate models for the province and determined cultivation using a multi-criterion, decision-based model that integrates AHP-PCA and GIS. We mapped the environmentally suitable areas for potato cultivation at a 3-km resolution based on the geo-climate model for each time period and analyzed differences between them. We found that "Most suitable” areas for potato cultivation are mainly distributed in the central area of Jilin Province, “Suitable” areas were located in the northwestern plains, and “Sub-suitable” areas in the eastern mountainous areas. In contrast, “Not suitable” areas occur mainly in the high-altitude areas in the east. The areas of “Most suitable” and “Suitable” areas for potato cultivation in Jilin Province are increasing, with increasing rates of 0.37 × 1,000 km² decade− 1 (R2 = 0.58, P < 0.01) and 0.20 × 1,000 km² (R2 = 0.28, P < 0.01), respectively, while the extent of “Sub-suitable” areas is decreasing, with a decreasing rate of 0.58 × 1,000 km² decade− 1 (R2 = 0.53, P < 0.05). The area of “Not suitable” areas has undergone little change. “Most suitable” and “Suitable” areas for potato cultivation showed a trend towards northward expansion. Overall, our results suggest that global climate change has had a positive impact on potato cultivation in Jilin Province over the past 58 years.

The growth rate hypothesis (GRH) proposes that higher growth rate (the rate of change in biomass per unit biomass, μ) is associated with higher P concentration and lower C:P and N:P ratios. However, the applicability of the GRH to vascular plants is not well-studied and few studies have been done on belowground biomass. Here we showed that, for aboveground, belowground and total biomass of three study species, μ was positively correlated with N:C under N limitation and positively correlated with P:C under P limitation. However, the N:P ratio was a unimodal function of μ, increasing for small values of μ, reaching a maximum, and then decreasing. The range of variations in μ was positively correlated with variation in C:N:P stoichiometry. Furthermore, μ and C:N:P ranges for aboveground biomass were negatively correlated with those for belowground. Our results confirm the well-known association of growth rate with tissue concentration of the limiting nutrient and provide empirical support for recent theoretical formulations.