Responses Of Nutrient Resorption Research Articles

Nitrate and Ammonium Nitrogen Addition Did Not Alter Nutrient Resorption of Dominant Plant in an Alpine Grassland

Worldwide increases in nitrogen deposition rates are influenced by human activities. Although the total amount of N deposition tends to be stable in our country, atmospheric N deposition of the reactive N forms (NO4+-N, NH4+; NO3−-N, NO3−) is remarkably different, and the ratios of NH4+ to NO3− change continuously. Nutrient resorption is a crucial driver of plant nutrient conservation strategies and litter quality. Therefore, the plant nutrient resorption pattern has remarkable ecological significance for nutrient cycling and the community structure of the ecosystem. However, previous studies have found that plants have different preferences in NH4+ and NO3−, and the response of nutrient resorption to different N forms remains unclear. In 2017 and 2018, we conducted field experiments simulating five NO3− and NH4+ addition ratios to examine the responses of the nutrient resorption of the dominant species, Stipa capillata, in the alpine grassland of northwest China. Results showed that N addition treatments did not affect the nutrient resorption efficiencies. The results showed that N application had little effect on soil inorganic N composition, so there was no significant change in the nutrient resorption efficiencies. In addition, the nutrient resorption efficiencies were unaffected across the five different ratios of nitrate and NH4+ addition, suggesting that nutrient resorption was not only controlled by the nutrient supply and nutrient form. Our results have important implications in understanding the significance of the frequency of N addition due to N loss through leaching and denitrification. The results also highlight that low intensity and high frequency N addition are required to investigate the response of plant nutrient resorption to the N supply in the future study.

Responses of nutrient resorption to interannual precipitation variability and nitrogen addition in a pine plantation

AbstractPlant nutrient concentration and resorption play a major role in determining primary production and development of forests. Yet how plant nutrient concentration and resorption respond to altered interannual precipitation and how interannual precipitation variability mediates the responses of plant nutrient concentration and resorption to N addition remain uncertain. Here, we examined the responses of needle nutrient (N and P) concentrations of all aged classes, nutrient resorption efficiency, and proficiency to N addition (10 g N m−2 year−1) over a 4‐year period (from 2016 to 2019) that experienced high variability in precipitation in a Mongolian pine plantation in a semiarid region of northeast China. There were significant interannual variations in N and P concentrations in all aged needles and litters, N and P resorption efficiency, as well as soil inorganic N and available P concentrations in the control plots. Increased precipitation resulted in increased needle nutrient concentrations across the four consecutive years. However, needle nutrient concentrations did not covary with soil available nutrients. The responses of needle N resorption efficiency (NRE) to N addition differed across the four years, with N addition decreasing NRE in wet years, but not in dry years. Taken together, our results showed that foliar nutrient concentrations are sensitive to altered annual precipitation and that different interaction effects exist between N addition and sampling year for different nutrient variables. Such differential responses highlight the challenge of predicting effects of N addition on nutrient cycling over temporal scales.

Conserved responses of nutrient resorption to extreme drought in a grassland: The role of community compositional changes

Abstract The frequency, duration and magnitude of drought are projected to increase in the next few decades, with consequences for community composition and nutrient utilization of plants. Nutrient resorption, a process facilitating plant nutrient conservation, is a crucial driver for ecosystem nutrient cycling. It remains unknown how would extreme drought affect nutrient resorption of plant communities through changing community composition. We examined the contributions of different processes (richness and identity effect of species losses and species gains, as well as the context dependent effect) related with community compositional changes to the alterations of community‐level nutrient resorption efficiency after 4‐year treatments of chronic drought (66% rainfall reduction from May to August) and intense drought (100% rainfall reduction in June and July) in a temperate steppe in Hulun Buir, Inner Mongolia, China. Both chronic and intense drought significantly reduced nutrient resorption efficiency in most of the common species, but did not affect that at the community level. Drought‐induced losses of species made positive contribution to the community‐level nutrient resorption, as they generally had lower nutrient resorption efficiency. Such positive contribution balanced the negative effect of drought on the nutrient resorption of the common species. Our results indicate that drought‐induced changes in community composition, especially those species being lost, were important in mediating the community‐level responses of nutrient resorption to extreme drought in grasslands. Read the free Plain Language Summary for this article on the Journal blog.

Responses of Nutrient Resorption to Human Disturbances in Phoebe bournei Forests

Nutrient resorption plays an important role in the nutrient conservation of plants and ecosystem nutrient cycling. Although community succession and nutrient addition could regulate plant nutrient resorption, how resorptions of foliar nutrients vary with human disturbances remains unclear. With the economic development, Phoebe bournei forests (PF) have suffered varying degrees of human disturbances in China. In this study, the leaf nutrient resorption efficiency (RE) of the PF under two disturbances (i.e., severe and mild disturbances) were investigated. Results showed that the phosphorus (P) contents of green leaf, senesced leaf, and soil were low under both disturbances, reflecting that the PF had a potential P limitation. Phosphorus and potassium (K) REs were higher under the severe disturbance than those under the mild disturbance. The potassium resorption efficiency was the highest among the three REs under both disturbances. In addition, nutrient resorption efficiencies increased with green leaf nutrient contents under both disturbances. However, there were negative significant relationships of specific leaf area and leaf dry matter content with nutrient resorption under both disturbances. These findings provide a new perspective of nutrient resorption and revealed the potential impact of human disturbances on the nutrient cycle in forest ecosystems.

Response of nutrient resorption of Leymus chinensis to nitrogen and phosphorus addition in a meadow steppe of northeast China.

Nutrient resorption, one of the most important strategies for plant nutrient conservation, is significantly affected by soil fertility. However, the effects of experimentally altered soil fertility on plant N and P resorption are poorly understood. The potential nutrient resorption response mechanisms of the dominant species Leymus chinensis to six N addition levels (0, 2.5, 5, 10, 20 and 40g·N·m-2 ·year-1 ), two P addition levels (0 and 10gP·m-2 ·year-1 ) and their interactions were studied after 3years of treatments in a temperate meadow steppe. In both green leaves and culms, N and P addition significantly increased N and P concentrations, respectively. Nitrogen addition led to a decrease in the N resorption efficiency (NRE) of both leaves and culms. Within each N treatment, P addition decreased the P resorption efficiency (PRE) of both leaves and culms and the NRE of leaves, except in the N2.5 treatment. Both NRE and PRE in leaves were higher than those in culms under N and P addition conditions. The nutrient concentrations and resorption efficiency were significantly correlated with the soil nutrient availability. Our results suggest that plants rely more on nutrient absorption from the soil, reducing the proportion of elements obtained through nutrient resorption in nutrient-rich environments.

Impacts of drought and nitrogen enrichment on leaf nutrient resorption and root nutrient allocation in four Tibetan plant species

Plant nutrient resorption, a process by which plant withdraws nutrients from senescing structures to developing tissues, can significantly affect plant growth, litter decomposition and nutrient cycling. Global change factors, such as nitrogen (N) deposition and altered precipitation, may mediate plant nutrient resorption and allocation. The ongoing global change is accompanied with increased N inputs and drought frequency in many regions. However, the interactive effects of increased N availability and drought on plant nutrient-responses remain largely unclear. In a pot experiment, we examined the impacts of N enrichment and drought on leaf N and phosphorous (P) resorption and root nutrient allocation in four species from the Qinghai-Tibet Plateau, including two graminoid species (Kobresia capillifolia and Elymus nutans) and two forb species (Delphinium kamaonense and Aster diplostephioides). Our results showed divergent resorption patterns within the two functional groups. E. nutans and D. kamaonense showed stronger N resorption than K. capillifolia and A. diplostephioides. N addition did not alter their N resorption efficiencies, but decreased the N resorption proficiencies of the former two species. In contrast, drought did not affect N or P resorption proficiencies, but decreased N resorption efficiency of K. capillifolia. Besides, N addition facilitated P resorption in K. capillifolia and D. kamaonense, and drought did the same in A. diplostephioides, suggesting that P resorption plays an important role in nutrient conservation in these species. Moreover, species with stronger N resorption allocated more biomass C or N to aboveground and enhanced their litter quality under N enrichment, while species with weaker resorption allocated more biomass C and/or N to belowground part under drought. Together, these results show that the responses of nutrient resorption and allocation to N enrichment and drought are highly species-specific. Future studies should take these differential responses into consideration to better predict litter decomposition and ecosystem nutrient cycling.

Nitrogen and phosphorus fertilizations alter nitrogen, phosphorus and potassium resorption of alfalfa in the Loess Plateau of China

Nutrient resorption from senescing leaves is a pivotal component of nutrient conservation strategy in a plant. Thus understanding the response of nutrient resorption to fertilization is of great help to minimize fertilizer use and further optimize fertilization management. However, little is known about how nutrient resorption responds to fertilization in N2-fixing species. Nitrogen (N) and phosphorus (P) fertilizers were applied at different rates to alfalfa stands in the Loess Plateau. N fertilization hardly affected leaf N and K resorptions, but tended to increase P resorption. P fertilization increased N and K resorptions but affected P resorption in various ways. However, effect of N or P fertilization was significantly interplayed by P or N rate. At N100P60, alfalfa had the maximum biomass accumulation and less leaf resorption. Therefore, alfalfa could be performed well with 100 kg N ha−1 and 60 kg P2O5 ha−1 in this region.

The species-specific responses of nutrient resorption and carbohydrate accumulation in leaves and roots to nitrogen addition in a subtropical mixed plantation

Ephemeral tissues such as leaves and fine roots are sensitive to nutrient alteration. Whether nutrient addition can influence the linkage between nutrient resorption and carbohydrate accumulation in leaves and roots is not clear. We measured nitrogen (N) and phosphorus (P) concentrations and nonstructural carbohydrates (NSC) of the <one- and >one-year-old leaves and absorptive and transportive roots in two species of a mixed plantation during the dormant and growing seasons within an N-addition experiment. Nitrogen addition decreased N and P resorption efficiencies (NRE and PRE, respectively) in leaves of Chinese fir and increased PRE in absorptive roots of Chinese fir but did not alter either efficiency in any tissues of Chinese sweetgum. Nitrogen addition increased starch accumulation efficiency (STAE) in >one-year-old leaves of Chinese fir but decreased soluble sugar accumulation efficiency (SSAE) in absorptive roots of Chinese sweetgum. Both NRE and PRE were negatively correlated with SSAE, STAE, and NSC accumulation efficiency (NSCAE) in >one-year-old leaves of Chinese fir, but this pattern was not found in leaves of Chinese sweetgum. Our study indicates that N addition can influence the linkage between nutrient resorption and NSC in leaves and roots, and this response to nutrient availability is species-dependent.

Responses of nutrient resorption to warming and nitrogen fertilization in contrasting wet and dry years in a desert grassland

As global climate warms and atmospheric nitrogen deposition increases, plants are likely to respond by altering community composition, thus affecting the nutrient cycle. Although it is well-known that feedback between plants and soils is linked by nutrient resorption occurring during senescence, our understanding of how long-term warming and nitrogen deposition (> 10 years) influence nutrient resorption remains limited. In a desert grassland in northern China, we explored the effects of warming and nitrogen fertilization on leaf nutrient resorption for three dominant species during two hydrologically contrasting years (wet with 52% above the long-term mean precipitation of 222 mm, and dry with precipitation 16% below the mean), based on a manipulative experiment initiated in 2006. In the wet year, both warming and nitrogen fertilization significantly increased nitrogen and phosphorus concentrations in soils and plants and thus decreased resorption efficiency of both nitrogen and phosphorus with significant interactions, but these effects did not occur in the dry year. Changes in resorption efficiency were associated with plant available nitrogen and phosphorus in soils and water availability. Our study suggests that the responses of nutrient resorption to warming and nitrogen fertilization could be modified by natural precipitation variations in a desert grassland that is sensitive to abrupt changes in weather patterns.

Does foliar nutrient resorption regulate the coupled relationship between nitrogen and phosphorus in plant leaves in response to nitrogen deposition?

Nutrient resorption from senescing leaves is an important process of internal nutrient cycling in plants, but the patterns of nutrient resorption and the coupled relationship between nitrogen (N) and phosphorus (P) in plant leaves as affected by N deposition remain unclear. We analysed the effects of N addition on the nutrient resorption and coupled relationship between N and P in plant leaves under different nutrient-limited conditions based on a global meta-analysis. Globally, the mean N resorption efficiency (NRE) and P resorption efficiency (PRE) under natural conditions were 47.4% and 53.6%, respectively, which were significantly regulated by geographical and climatic factors as well as plant characteristics. Furthermore, N addition significantly decreased the NRE by 13.3% but slightly affected the PRE on a global scale, and N addition rates and latitude directly and negatively affected the effects of N addition on NRE. Specifically, N addition significantly decreased the NRE under all nutrient-limited conditions, while it had negative, positive, and neutral effects on the PRE under N-limited, P-limited, and N and P-co-limited conditions, respectively. Moreover, the relationships between N and P in green and senesced leaves were tightly coupled under different nutrient-limited conditions in natural ecosystems. However, N addition significantly weakened the relationships between N and P concentrations in green leaves but slightly affected the relationship in senesced leaves, which were mainly modulated by the effects of N addition on nutrient resorption efficiency, especially NRE. These results highlight that nutrient-limited conditions determine the response of nutrient resorption to N deposition and emphasize the effect of nutrient resorption regulation on the coupling of N and P responses to N enrichment. The findings are important for understanding plant nutrient use strategies and the mechanisms underlying the stoichiometric coupling of N and P in response to climate change, and can be used in global biogeochemical models.

Stage-dependent stoichiometric homeostasis and responses of nutrient resorption in Amaranthus mangostanus to nitrogen and phosphorus addition.

Stoichiometric homeostasis is the ability of plants remaining their element composition relatively stable regardless of changes in nutrient availability, via various physiological mechanisms. Nutrient resorption is one of such key mechanisms, but whether and how nitrogen and phosphorus homeostasis and resorption in plants would change with growth-stages under variable nutrient supply was unclear. A nitrogen (N) and phosphorus (P) fertilizer addition experiment was conducted to evaluate the dynamics of N and P homeostasis and resorption efficiency during different growth-stages of Amaranthus mangostanus in a greenhouse. The homeostasis regulation coefficient of green-leaf P varied significantly, while that of green-leaf N maintained relatively stable across growth stages. Moreover, homeostasis regulation coefficient of N was higher at seedling stage but lower at flowering stage than that of P at corresponding stages, suggesting that the growth of A. mangostanus may switch from being more N- to P-limited from vegetative to reproductive stage. N resorption efficiency (NRE) was higher and P resorption efficiency (PRE) was lower at flowering than seed-filling stage. The nutrient dynamics displayed here suggested contrasting nutrient homeostasis and resorption responses of plants to environmental nutrient availability across growth stages. These findings can improve the understanding of nutrition maintenance mechanism of plants during their growth.

Responses of plant nutrient resorption to phosphorus addition in freshwater marsh of Northeast China.

Anthropogenic activities have increased phosphorus (P) inputs to most aquatic and terrestrial ecosystems. However, the relationship between plant nutrient resorption and P availability is still unclear, and much less is known about the underlying mechanisms. Here, we used a multi-level P addition experiment (0, 1.2, 4.8, and 9.6 g P m−2 year−1) to assess the effect of P enrichment on nutrient resorption at plant organ, species, and community levels in a freshwater marsh of Northeast China. The response of nutrient resorption to P addition generally did not vary with addition rates. Moreover, nutrient resorption exhibited similar responses to P addition across the three hierarchical levels. Specifically, P addition decreased nitrogen (N) resorption proficiency, P resorption efficiency and proficiency, but did not impact N resorption efficiency. In addition, P resorption efficiency and proficiency were linearly related to the ratio of inorganic P to organic P and organic P fraction in mature plant organs, respectively. Our findings suggest that the allocation pattern of plant P between inorganic and organic P fractions is an underlying mechanism controlling P resorption processes, and that P enrichment could strongly influence plant-mediated biogeochemical cycles through altered nutrient resorption in the freshwater wetlands of Northeast China.

Effects of fertilisation and irrigation on ‘foliar afterlife’ in alpine tundra

AbstractQuestion:How do increases in soil nutrient and water availability alter the nutrient fluxes through the resorption and litter decomposition pathways and how do they affect litter nutrient pools in a low‐productive alpine tundra ecosystem?Location:An alpine lichen‐rich tundra on Mt. Malaya Khati‐para in the NW Caucasus, Russia (43°27’ N, 41°42’ E; altitude 2800 m a.s.l.).Methods:We conducted a 4‐year fertilisation (N, P, N+P, lime) and irrigation experiment, and analysed the responses of nutrient resorption from senescing leaves, leaf litter quality and decomposability of six pre‐dominant vascular plant species, total plant community litter production and litter (nutrient) accumulation.Results:Vascular plant litter [N] and [P] increased 1.5 and 10 fold in response to N and P additions, due to increased concentrations of the nutrients in fresh leaves and unchanged or reduced resorption efficiency. Litter decomposability was not affected by nutrient amendments. Fertilisation enhanced litter production (180%; N+P treatment) and litter accumulation (80%; N+P), owing to tremendously increased production and low decomposability of graminoids. Together with increased litter [N] and [P] this led to great increases in total litter nutrient pools.Conclusions:Due to increased production of graminoids, nutrients added to the alpine tundra soil were mostly immobilised in recalcitrant, nutrient‐rich litter. This suggests that changing species composition in low productive ecosystems may act as an internal buffer mechanism, which under increased soil nutrient availability prevents the community from rapidly acquiring features typical of a high productive ecosystem such as high decomposability and high nutrient availability.

Effects of fertilisation and irrigation on ‘foliar afterlife’ in alpine tundra

Question: How do increases in soil nutrient and water availability alter the nutrient fluxes through the resorption and litter decomposition pathways and how do they affect litter nutrient pools in a low-productive alpine tundra ecosystem? Location: An alpine lichen-rich tundra on Mt. Malaya Khati-para in the NW Caucasus, Russia (43°27’ N, 41°42’ E; altitude 2800 m a.s.l.). Methods: We conducted a 4-year fertilisation (N, P, N+P, lime) and irrigation experiment, and analysed the responses of nutrient resorption from senescing leaves, leaf litter quality and decomposability of six pre-dominant vascular plant species, total plant community litter production and litter (nutrient) accumulation. Results: Vascular plant litter [N] and [P] increased 1.5 and 10 fold in response to N and P additions, due to increased concentrations of the nutrients in fresh leaves and unchanged or reduced resorption efficiency. Litter decomposability was not affected by nutrient amendments. Fertilisation enhanced litter production (180%; N+P treatment) and litter accumulation (80%; N+P), owing to tremendously increased production and low decomposability of graminoids. Together with increased litter [N] and [P] this led to great increases in total litter nutrient pools. Conclusions: Due to increased production of graminoids, nutrients added to the alpine tundra soil were mostly immobilised in recalcitrant, nutrient-rich litter. This suggests that changing species composition in low productive ecosystems may act as an internal buffer mechanism, which under increased soil nutrient availability prevents the community from rapidly acquiring features typical of a high productive ecosystem such as high decomposability and high nutrient availability.