Shifting phenology and abundance under experimental warming alters trophic relationships and plant reproductive capacity

Phenological mismatches due to climate change may have important ecological consequences. In a three-year study, phenological shifts due to experimental warming markedly altered trophic relationships between plants and insect herbivores, causing a dramatic decline of reproductive capacity for one of the plant species. In a Tibetan meadow, the gentian (Gentiana formosa) typically flowers after the peak larva density of a noctuid moth (Melanchra pisi) that primarily feeds on a dominant forb (anemone, Anemone trullifolia var. linearis). However, artificial warming of 1.5°C advanced gentian flower phenology and anemone vegetative phenology by a week, but delayed moth larvae emergence by two weeks. The warming increased larval density 10-fold, but decreased anemone density by 30%. The phenological and density shifts under warmed conditions resulted in the insect larvae feeding substantially on the gentian flowers and ovules; there was 100-fold more damage in warmed than in unwarmed chambers. This radically increased trophic connection reduced gentian plant reproduction and likely contributed to its reduced abundance in the warmed chambers

Soil Seed Bank and Plant Community Development in Passive Restoration of Degraded Sandy Grasslands

To evaluate the efficacy of passive restoration on soil seed bank and vegetation recovery, we measured the species composition and density of the soil seed bank, as well as the species composition, density, coverage, and height of the extant vegetation in sites passively restored for 0, 4, 7, and 12 years (S0, S4, S7, and S12) in a degraded grassland in desert land. Compared with S0, three more species in the soil seed bank at depths of 0–30 cm and one more plant species in the community was detected in S12. Seed density within the topsoil (0–5 cm) was five times higher in S12 than that in S0. Plant densities in S7 and S12 were triple and quadruple than that in S0. Plant coverage was increased by 1.5 times (S4), double (S7), and triple (S12) compared with S0. Sørensen’s index of similarity in species composition between the soil seed bank and the plant community were high (0.43–0.63), but it was lower in short-term restoration sites (S4 and S7) than that in no and long-term restoration sites (S0 and S12). The soil seed bank recovered more slowly than the plant community under passive restoration. Passive restoration is a useful method to recover the soil seed bank and vegetation in degraded grasslands

Shifting plant leaf anatomical strategic spectra of 286 plants in the eastern Qinghai-Tibet Plateau: Changing gears along 1050–3070 m

Leaf anatomical traits can reflect plant adaptation to environmental changes. However, whether the trade-offs among leaf anatomical traits can reflect the strategies spectrum of plant response to environmental changes and the strategic spectrum will shift with altitudes are not clear. In this study, 286 plant species from 19 altitudinal gradients from 1050 m to 3070 m on the eastern Tibetan Plateau were selected and 16 anatomical characters of blade, mesophyll and midrib were measured. The strategic spectra of leaf anatomical trait formation were studied by the principal components analysis, followed by generalized additive models of the strategic spectra with shift in elevation to test the shift of strategy spectra along altitudes. There are differences in response mode and intensity between woody plants and herbaceous plants along altitudes. Blade strategic spectrum (BSS), blade and mesophyll strategic spectrum (BMSS) and midrib strategic spectrum (MSS) were formed in the tissue of leaves, and the score of principal component one (PC1) was not significant between herbs and woody plants (P > 0.05). There was mainly the spectrum of conservation and supported strategies and the spectrum of resource acquisition and consumption. With increasing altitudes, the habita tended to become unsuitable for plant growth and the resources available to plants reduced. Consequently, the plants shifted from a “invest-fast-reap” acquisition strategy to a “invest-slow-reap” conservative strategy

Variability of Aboveground Litter Inputs Alters Soil Carbon and Nitrogen in a Coniferous–Broadleaf Mixed Forest of Central China

Global changes and human disturbances can strongly affect the quantity of aboveground litter entering soils, which could result in substantial cascading effects on soil biogeochemical processes in forests. Despite extensive reports, it is unclear how the variations in litter depth affect soil carbon and nitrogen cycling. The responses of soil carbon and nitrogen to the variability of litter inputs were examined in a coniferous⁻broadleaf mixed forest of Central China. The litter input manipulation included five treatments: no litter input, natural litter, double litter, triple litter, and quadruple litter. Multifold litter additions decreased soil temperature but did not affect soil moisture after 2.5 years. Reductions in soil pH under litter additions were larger than increases under no litter input. Litter quantity did not affect soil total organic carbon, whereas litter addition stimulated soil dissolved organic carbon more strongly than no litter input suppressed it. The triggering priming effect of litter manipulation on soil respiration requires a substantial litter quantity, and the impacts of a slight litter change on soil respiration are negligible. Litter quantity did not impact soil total nitrogen, and only strong litter fluctuations changed the content of soil available nitrogen (nitrate nitrogen and ammonium nitrogen). Litter addition enhanced soil microbial biomass carbon and nitrogen more strongly than no litter input. Our results imply that the impacts of multifold litter inputs on soil carbon and nitrogen are different with a single litter treatment. These findings suggest that variability in aboveground litter inputs resulting from environmental change and human disturbances have great potential to change soil carbon and nitrogen in forest ecosystems. The variability of aboveground litter inputs needs to be taken into account to predict the responses of terrestrial soil carbon and nitrogen cycling to environmental changes and forest management

Divergent impacts of drought on autumn phenology in China

Drought events occur frequently, but the impact of drought on plant autumn phenology, i.e., End of growing Season (EOS), has not been thoroughly studied. Considering that drought has cumulative and lagged effects on plants. In this study, we quantified two effects of drought on EOS in China. Our results indicated that cumulative and lagged affected 39.5% and 70.1% of plants EOS in China over the past two decades. Two effects of drought on short timescales (2- to 4-accumulated month and 1- to 5-lagged month) largely affected EOS of plants. Drought in the first two months of EOS advanced EOS, while drought in the fifth month before EOS caused plants to overcompensate for growth and delayed plant senescence. At the biome level, forests were more resistant to drought than grasslands and shrublands. From the perspective of the water balance gradient, drought was more significant in humid regions, and it was found that increased water loss exacerbated the effects of drought and shortened plant response time. Our study reveals the impact of drought on plant autumn phenology and provides insights into predicting future vegetation growth patterns under global change

Differences in Phenotypic Plasticity between Invasive and Native Plants Responding to Three Environmental Factors

The phenotypic plasticity hypothesis suggests that exotic plants may have greater phenotypic plasticity than native plants. However, whether phenotypic changes vary according to different environmental factors has not been well studied. We conducted a multi-species greenhouse experiment to study the responses of six different phenotypic traits, namely height, leaf number, specific leaf area, total biomass, root mass fraction, and leaf mass fraction, of native and invasive species to nutrients, water, and light. Each treatment was divided into two levels: high and low. In the nutrient addition experiment, only the leaf mass fraction and root mass fraction of the plants supported the phenotypic plasticity hypothesis. Then, none of the six traits supported the phenotypic plasticity hypothesis in the water or light treatment experiments. The results show that, for different environmental factors and phenotypes, the phenotypic plasticity hypothesis of plant invasion is inconsistent. When using the phenotypic plasticity hypothesis to explain plant invasion, variations in environmental factors and phenotypes should be considered

Appendix A. Schematic diagram showing trophic relationships among the moth larvae (Melanchra pisi) and the two plant species Gentiana formosa and Anemone trullifolia var. linearis.

Schematic diagram showing trophic relationships among the moth larvae (Melanchra pisi) and the two plant species Gentiana formosa and Anemone trullifolia var. linearis

Data from: Effects of nitrogen addition and mowing on rodent damage in an Inner Mongolian steppe

Rodent damage is a serious threat to sustainable management of grassland. The effects of nitrogen (N) deposition and grassland management on rodent damage have been scarcely studied. Here, we reported the effects of two years of N addition and mowing on burrow density and damage area of Citellus dauricus in a semi-arid steppe in Inner Mongolia. N addition significantly aggravated, while mowing alleviated rodent damage in the grassland under study. Burrow density and damage area increased 2.8- and 4.7-fold, in N addition plots compared to the ambient N addition treatment, respectively. Conversely, mowing decreased burrow density and damage area by 75.9% and 14.5%, respectively, compared to no mowing plots.. Observed changes in rodent damage were mainly due to variations in plant community cover, height, and aboveground net primary productivity. Our findings demonstrate that N addition and mowing can affect the rodent density and activity in grassland, suggesting that the effects of a changing atmospheric composition and land use on rodent damage must be considered in order to achieve better grassland management

Synthetic nitrogen fertilizers alter the soil chemistry, production and quality of tea. A meta-analysis

The intensive use of synthetic nitrogen fertilizers over the last century has both increased agricultural productivity and modified biogeochemical cycles in terrestrial ecosystems, causing severe negative environmental impacts. Tea (Camellia sinensis L.) plantations usually receive high levels of synthetic fertilizers, which strongly affect plant and soil properties. However, there is no quantitative study to assess how synthetic N additions affect soil chemistry and the production and quality of tea shoots. Here, we conducted a comprehensive meta-analysis to evaluate the effects of experimental synthetic N fertilizers. Our main findings are (1) N additions in tea plantations acidify soils (-0.41 pH unit in average) and produce soil nutrient imbalance. Soil acidification commonly exacerbates the accumulations of toxic aluminum ions. (2) Synthetic N fertilizer additions may strongly increase tea production by almost 70% but alter tea shoot quality by increasing the concentrations of free amino acids (+ 16%), caffeine (+ 14%), and water extracts (+ 5%) while decreasing those of soluble sugars (-8%) in the tea shoots. The responses of soil chemistry, tea production, and quality to N additions can vary among experimental conditions, tea tree species, and N fertilizer forms. Because there is statistical limitation in this meta-analysis, our findings recommend performing additional field studies to explore the potential mechanisms of nutrient cycling and ecosystem functioning under synthetic N additions. The development of a sustainable N management strategy in tea plantations is also urgently needed to enhance N use efficiency and reduce environmental risks