Plant Primary Production Research Articles

Spectral unmixing of hyperspectral images revealed pine wilt disease sensitive endmembers.

Throughout the entire cycle of leaf phenological events, leaf colour undergoes changes that are influenced by either abiotic stress or biotic infection. These changes in colouration are closely linked to the quantity and quality of photosynthetic pigments, which directly impact the primary productivity of plants. Therefore, monitoring and quantifying leaf colouration changes are crucial for distinguishing damage caused by pine wilt nematodes from natural tree senescence. In this study, a hyperspectral camera sensor was employed for the non-invasive and non-destructive evaluation of needle colour changes in coniferous trees grown in field tests. Three distinct needle colour variations of six coniferous tree species were selected and monitored using a hyperspectral sensor: those displaying seasonal autumn colours, undergoing nematode-infected necrosis processes, and experiencing natural death. To mitigate the inherently mixed spectral properties of hyperspectral data, endmembers were extracted from individual images using the Purity Pixel Index algorithm under the assumption of linear mixing of endmembers. From a total of 1,321 endmembers extracted from 378 hyperspectral images of six pine species, eight endmembers were ultimately chosen to reconstruct hyperspectral images and generate abundance maps. Among these eight endmembers, four represent varying levels of photosynthetic pigment contents-ranging from very low to high. Consequently, these coniferous endmembers hold promise for assessing seasonal leaf phenology and the extent of damage in pine trees infected by pine wilt nematodes. This comprehensive approach underscores the effectiveness of spectral unmixing of hyperspectral images in advancing precision forestry through meticulous coniferous needle trait analysis.

Cascading effects driven by population recovery of sika deer on habitat use of sympatric mammals under heavy snow conditions

AbstractUnlike the top‐down cascading effects driven by apex predators, the bottom‐up effects on biological interactions originating from herbivory by large mammals, especially within mammalian assemblages, have received less attention. This study aimed to identify the multifaceted impacts driven by sika deer (Cervus nippon) during midwinters, when their herbivory impacts were expected to be strong due to deficient dietary resources. We focused on interference and exploitative competition caused by deer on the habitat use of four sympatric mammal species, namely two herbivores (Japanese serow, Capricornis crispus, and Japanese hare, Lepus brachyurus angustidens) and two mesocarnivores (red fox, Vulpes vulpes, and Japanese marten, Martes melampus melampus). To estimate the wintering behaviors of these mammals and deer herbivory pressure, we performed snow tracking and counted the fresh feeding marks of deer during midwinter in 2022 and 2023. We conducted surveys on 201‐km transects with different stages of deer population recovery (i.e., different deer population densities) in heavy snowfall regions of Japan. We then systematically quantified the deer‐driven effects on sympatric mammals using piecewise structural equation modeling (SEM). We recorded 1700 tracks of target mammals and 1327 trees with deer feeding marks. Based on these records, we constructed an SEM with acceptable performance (Fisher's C = 27.1, P = 0.30). The SEM suggested some possibilities that exploitative competition mediated by deer herbivory constrained the habitat use of mammals with dietary habits similar to that of deer, i.e., serow (effect size, −0.13) and hares (−0.14). In addition, through constricting the habitat use of hares, the deer‐driven cascading effects reduced the occurrence of their key predators, i.e., foxes (−0.12) and martens (−0.10). Thus, our observations provide novel evidence that food webs are regulated by herbivore‐driven bottom‐up cascading effects in cases where plant primary productivity is limited by heavy snowfall.

A hysteretic response of the global carbon cycle to anthropogenic СО<sub>2</sub> emissions into the atmosphere

Idealized numerical experiments were performed with the Earth system model developed at the A. M. Obukhov Institute of Atmospheric Physics of the Russian Academy of Sciences (IAP RAS ESM) under anthropogenic CO2 emissions into the atmosphere, which increase initially and decrease afterwards. These numerical experiments revealed the inertia of various components of the Earth system, leading to a delay in the response of various components of the carbon cycle relative to the anthropogenic emissions by several decades. The inertia of the carbon cycle components leads to a hysteresis response of its characteristics to non-monotonic in time anthropogenic CO2 emissions into the atmosphere, noticeable, in particular, for the gross primary production and respiration of plants and soil. In turn, the hysteretic response of the characteristics of the global carbon cycle indicates the irreversibility of its changes on the scale of (at least) several decades. The latter should be taken into account when planning adaptation and/or mitigation of climate change.

Seabird guano inputs increase impacts from introduced mammals on the native plants and animals of an oceanic island.

Seabirds create fluxes of nutrients from marine to terrestrial ecosystems that influence the food webs of small islands. We investigated how guano inputs shape terrestrial food webs by comparing species of selected plant and animal species in a red-footed booby colony in Mona Island (Puerto Rico, Caribbean Sea), to sites of the island lacking guano inputs. We quantified guano deposition and its relationship to plant biomass production, fecundity and density, as well as the activity of native and introduced animal species. In general, guano inputs increased the gross primary plant productivity, size, and fecundity by twofold. Guano inputs were also associated with twofold increases in density of Anole lizards, but also to increases in the activity of introduced pigs (> 500%), goats (> 30%), and cats (> 500%), which negatively impact native species. In particular, elevated pig and cat activity within the booby colony was correlated with lower activity of endemic ground lizards and of introduced rats. Our results also suggest that severe droughts associated with climate change exacerbate the negative effects that introduced species have on vegetation and reduce the positive effects of seabird guano inputs. Our findings underscore the importance of allochthonous guano inputs in subsidizing plant productivity and native and endemic species in small oceanic islands, but also in increasing the negative impacts of introduced mammals. Management and conservation efforts should focus on the exclusion (or eradication) of introduced mammals, particularly pigs and goats, from remnant seabird colonies in Mona Island.

Interplay of soil characteristics and arbuscular mycorrhizal fungi diversity in alpine wetland restoration and carbon stabilization.

Alpine wetlands are critical ecosystems for global carbon (C) cycling and climate change mitigation. Ecological restoration projects for alpine grazing wetlands are urgently needed, especially due to their critical role as carbon (C) sinks. However, the fate of the C pool in alpine wetlands after restoration from grazing remains unclear. In this study, soil samples from both grazed and restored wetlands in Zoige (near Hongyuan County, Sichuan Province, China) were collected to analyze soil organic carbon (SOC) fractions, arbuscular mycorrhizal fungi (AMF), soil properties, and plant biomass. Moreover, the Tea Bag Index (TBI) was applied to assess the initial decomposition rate (k) and stabilization factor (S), providing a novel perspective on SOC dynamics. The results of this research revealed that the mineral-associated organic carbon (MAOC) was 1.40 times higher in restored sites compared to grazed sites, although no significant difference in particulate organic carbon (POC) was detected between the two site types. Furthermore, the increased MAOC after restoration exhibited a significant positive correlation with various parameters including S, C and N content, aboveground biomass, WSOC, AMF diversity, and NH4+. This indicates that restoration significantly increases plant primary production, litter turnover, soil characteristics, and AMF diversity, thereby enhancing the C stabilization capacity of alpine wetland soils.

Nitrogen and phosphorus additions alter foliar nutrient concentrations of dominant grass species and regulate primary productivity in an Inner Mongolian meadow steppe

Excessive nitrogen (N) inputs shift grassland productivity from nitrogen (N) to phosphorus (P) limitation. However, how plant nutrient concentrations and stoichiometric dynamics at community and species level responding to variable soil N and P availability, and their roles in regulating net primary productivity in meadow steppe remain unclear. To address this issue, we carried out an experiment with fifteen treatments consisting of factorial combinations of N (0, 1.55, 4.65,13.95, 27.9 g N m−2 yr−1) and P (0, 5.24,10.48 g P m−2 yr−1) for three years in a meadow steppe in Inner Mongolia. We examined concentrations and stoichiometry of C (carbon), N, P in plants and soils, and their associations with plant primary productivity. Results revealed mean community N:P ratios for shoots (12.89 ± 0.98) did not exceed 14 within the control treatment, indicating that plant growth was primarily N-limited in this ecosystem. Shoot N:P ratios were significantly increased by N addition (>16 when N application rate above 4.65 g N m−2 yr−1), shifting the community from N- to P-limited whereas significantly reduced by P addition (N:P ratios <14), further aggravating N limitation. N addition increased leaf-N concentrations whereas decreased leaf C:N ratios of all four species, but only the values for two graminoid species were significantly influenced by P addition. Leaf-P concentrations significantly increased for graminoids but significantly decreased for forbs with the application of N. VPA analysis revealed that aboveground components, especially in grass leaves, explained more variation in aboveground net primary productivity (ANPP) and belowground net primary productivity (BNPP) than root and soil components. For grasses, leaf-N concentrations showed high association with ANPP, while leaf-P concentrations were associated with BNPP. These results highlight that N and P depositions could affect the leaf-nutrient concentrations of dominant grasses, and thereby potentially alter net primary productivity in meadow steppe.

Effects of rock lithology and soil nutrients on nitrogen and phosphorus mobility in trees in non-karst and karst forests of southwest China

The primary productivity of terrestrial plants is widely limited by nitrogen (N) and phosphorus (P), and the mobility of N and P in plants is the key to predicting plant growth and development. Non-karst and karst forests soil have different nutrient supply capacities due to the difference in soil parent material, but the effect mechanism of the two soil nutrient conditions on the N and P mobility process of trees remains unclear. In this study, forests dominated by three typical tree species, Eucalyptus maideni, Pinus yunnanensis, and Quercus franchetii were selected as the research objects in non-karst and karst areas of southwest China to investigate the effects of soil nutrient conditions on plants’ N and P foraging, transportation and resorption. The results showed that the rock lithology had significant effects on the soil nutrients, plants’ N and P foraging, transportation, and resorption. The soil total N and P concentrations, soil organic carbon concentration, and pH were higher in karst forests than those in the non-karst forests, but the green leaves N and P concentrations exhibited opposite characteristics. The root foraging potential for N and P in non-karst forests was significantly higher than that in karst forests. The N resorption efficiency of trees in karst forests was higher than that in non-karst forests, but the P resorption efficiency was lower than that in non-karst forests. The trade-offs of foraging, transportation and resorption of trees were adjusted according to changes in nutrient conditions, but the trade-offs of the three processes were not continuous in non-karst and karst forests. Compared with non-karst forests, the decreased degree of root nutrient foraging potential in karst forests was greater than the transportation factor and resorption efficiency. The slow-growing Quercus franchetii among the three typical forests showed better adaptability to foraging, transportation, and resorption of N and P in karst areas. The results revealed the response of different forests’ N and P mobility patterns of trees to different nutrient conditions in non-karst and karst areas, which was helpful to improve the prediction and mechanistic understanding of nutrient cycling in local forest ecosystems.

Nitrogen sources differentially affect respiration, growth, and carbon allocation in Andean and Lowland ecotypes of Chenopodium quinoa Willd.

Chenopodium quinoa Willd. is a native species that originated in the High Andes plateau (Altiplano) and its cultivation spread out to the south of Chile. Because of the different edaphoclimatic characteristics of both regions, soils from Altiplano accumulated higher levels of nitrate () than in the south of Chile, where soils favor ammonium (NH4 +) accumulation. To elucidate whether C. quinoa ecotypes differ in several physiological and biochemical parameters related to their capacity to assimilate and NH4 +, juvenile plants of Socaire (from Altiplano) and Faro (from Lowland/South of Chile) were grown under different sources of N ( or NH4 +). Measurements of photosynthesis and foliar oxygen-isotope fractionation were carried out, together with biochemical analyses, as proxies for the analysis of plant performance or sensitivity to NH4 +. Overall, while NH4 + reduced the growth of Socaire, it induced higher biomass productivity and increased protein synthesis, oxygen consumption, and cytochrome oxidase activity in Faro. We discussed that ATP yield from respiration in Faro could promote protein production from assimilated NH4 + to benefit its growth. The characterization of this differential sensitivity of both quinoa ecotypes for NH4 + contributes to a better understanding of nutritional aspects driving plant primary productivity.

Landscape heterogeneity increases the stability of wild ungulate populations facing climatic variability in Mediterranean ecosystems

Mediterranean environments are characterized by strong intra- and inter-annual fluctuations in plant primary production, which are likely to regulate the carrying capacity and density-dependent responses of ungulate populations. These effects may, however, vary across spatial and temporal scales. Habitat heterogeneity, particularly when associated to differentiated phenological responses, may allow wild ungulates to mitigate temporal fluctuations in plant production by using different resources along the year. In this work, we use a 15-years dataset (including remote-sensing data on vegetation distribution, phenology and production, as well as ungulate population counts) to assess how temporal variability in plant primary production and livestock abundance influence the population dynamics of two wild ungulates: native red deer, Cervus elaphus, and introduced fallow deer, Dama dama. Results show that temporal alternation in the phenological cycles of the four different vegetation types increased plant production, thus food availability for ungulates, within each year. Furthermore, complementarity in the responses of different vegetation types to variations in the amount and timing of rainfall increased the predictability of food availability across different years. This complementarity effect was further increased by the contrasting responses of ungulate populations to variation in the production of different vegetation types. Furthermore, domestic ungulates had positive effects on wild ungulate density at low to intermediate abundances, but high livestock densities decreased ungulate density and constrained the stability of the plant-ungulate system in response to the impact of climatic variation, particularly under climate change. Our findings deepen the knowledge on vegetation-ungulate interactions in Mediterranean areas, potentially contributing to develop better management strategies of ungulate populations and adapt them to ongoing climate change.

Incorporating biotic phosphorus-acquisition strategies into soil phosphorus transformation under long-term salinization in a tidal wetland

Tidal wetland plants can maintain high primary productivity under salinization, even with low phosphorus (P) availability. However, little is known about how they adapt to salinization-induced ecosystem P limitation over time. We established mesocosms using tidal freshwater wetland soils and the salt-tolerant plant Cyperus malaccensis and subjected them to short-term (6 months) and long-term (3.5 years) salinization. Overall, short-term salinization did not change plant or microbial biomass nitrogen/P ratios, whereas long-term salinization increased both, indicating that short-term salinization did not alter ecosystem P limitation, but long-term salinization exacerbated it. Concurrently, short-term salinization reduced the moderately labile inorganic P (Pi) pool, whereas long-term salinization also reduced the hydrolyzable organic P (Po) and primary mineral P pools. During both short- and long-term salinization, moderately labile Pi mobilization exhibited a negative correlation with Fe sulfide concentration and a positive correlation with Fe(III) concentrations. These results suggested that both short- and long-term salinization obtained P through abiotic P-acquisition strategies. Mobilization of the primary mineral P pool and hydrolyzable Po pools was negatively linked to root arbuscular mycorrhizal fungi (AMF) biomass and soil alkaline phosphomonoesterase (ALP) activity, respectively. This indicated that long-term salinization acquired P via biotic P-acquisition strategies. Specifically, soil microorganisms increased fungi predominance and thereby increased ALP activity to convert hydrolyzable Po, while tidal wetland plants enhanced root AMF associations to release carboxylate to transform primary mineral P. Overall, our results highlight that abiotic P-acquisition strategies could offset the ecosystem P limitation during short-term salinization, whereas biotic P-acquisition strategies play a more important role in soil P transformation under long-term salinization. Through biotic P-acquisition, tidal wetland ecosystems can maintain high plant primary productivity through biotic P-acquisition even under P-limited conditions, exhibiting increased resilience to sea-level rise.

Symbiosis of Arbuscular Mycorrhizal Fungi and Lycium barbarum L. Prefers NO3− over NH4+

Nitrogen (N) is an essential nutrient that plants require and is, most of the time, limited in different terrestrial ecosystems. Forming symbioses with plants, arbuscular mycorrhizal (AM) fungi improve mineral element uptake and the net primary production of plants. Recent reports have suggested that AM fungi mediate N uptake in plants. However, there are fewer studies on the influence of AM fungi on the response of Lycium barbarum, a medicinal plant in northwest China, under different N-addition conditions. In this study, the effect of Rhizophagus irregularis, N forms (NO3− and NH4+), and N levels (1.5, 7.5, 15, 30 mM) on the performance of L. barbarum was evaluated through a pot experiment. The application of R. irregularis significantly improved L. barbarum biomass, net photosynthetic rate, and root tissue viability under adequate NO3− and NH4+ supplies, and mycorrhizal plants showed better performance under NO3− supply. AM colonization enhanced N acquisition under adequate NO3− supply and strongly induced the expression of LbAMT3-1 in L. barbarum roots. Based on these results, we propose that NO3−-dominated N supply favors mycorrhizal symbiosis to a greater extent than NH4+; this study provides a basis for maintaining beneficial AM symbiosis during nitrogen fertilizer use in arable land.

Comprehensive Effects of Atmosphere and Soil Drying on Stomatal Behavior of Different Plant Types

The soil water supply and atmospheric humidity conditions are crucial in controlling plants’ stomatal behavior and water use efficiency. When there is water stress caused by an increase in saturated water vapor pressure (VPD) and a decrease in soil water content (SWC), plants tend to close stomata to reduce water loss. This affects the gross primary productivity (GPP) and evapotranspiration (ET), subsequently leading to changes in water use efficiency (WUE) and carbon use efficiency (CUE) in plants. However, land–atmosphere interactions mean that water vapor in the atmosphere and soil moisture content causing water stress for plants are closely related. This study aims to compare and estimate the effects of VPD and SWC on the carbon cycle and water cycle for different plant functional types. Based on the fluxnet2015 dataset from around the world, the WUE and CUE of five plant functional types (PFTs) were estimated under varying levels of VPD and SWC. The results showed that high VPD and low SWC limit the stomatal conductance (Gs) and gross primary productivity (GPP) of plants. However, certain types of vegetation (crops, broad-leaved forests) could partially offset the negative effects of high VPD with higher SWC. Notably, higher SWC could even alleviate limitations and partially promote the increase in GPP and net primary production (NPP) with increasing VPD. WUE and CUE were directly affected by Gs and productivity. In general, the increase in VPD in the five PFTs was the dominant factor in changing WUE and CUE. The impact of SWC limitations on CUE was minimal, with an overall impact of only −0.05μmol/μmol on the four PFTs. However, the CUE of savanna plants changed differently from the other four PFTs. The rise in VPD dominated the changes in CUE, and there was an upward trend as SWC declined, indicating that the increase in VPD and decrease in SWC promote the increase in the CUE of savanna plants to some extent.

Effects of Exiguobacterium sp. DYS212, a Saline-Alkaline-Tolerant P-Solubilizing Bacterium, on Suaeda salsa Germination and Growth

Soil nutrient availability under saline-alkali stress limits plant primary productivity. P-solubilizing bacteria (PSB) improve inorganic P dissolution and promote plant growth. However, the application studies of saline-alkaline-tolerant PSB are still scarce. We isolated one PSB strain from bird droppings in saline-alkali regions and identified its growth characteristics and resistance to salt and alkali. A potting experiment with PSB addition was performed to analyze the effect of this strain on the germination and growth of Suaeda salsa. The PSB were identified as Exiguobacterium sp. DYS212 strain, and it utilized glucose, ammonium sulfate, and yeast extract powder well. The strain is halophilic, has the ability to dissolve inorganic P, and improved P-solubilization under 1–5.5% salinity (available P &gt; 200 mg L−1), reached a maximum at 2.5% NaCl concentration yielding 410.73 mg L−1 of available P. The PSB promoted seed germination, especially under high alkaline stress, wherein the growth promoting rate increased to 5.26%. The PSB improved the growth of S. salsa, in terms of plant height, stem diameter, and biomass (up to 2.5 times), under saline and alkaline conditions. This study highlights the potential of Exiguobacterium sp. isolates as biofertilizers, and provides reference for environment sustainability of saline-alkali region.

Recent Acceleration of Wetland Accretion and Carbon Accumulation Along the U.S. East Coast

AbstractThe long‐term stability of coastal wetlands is determined by interactions among sea level, plant primary production, sediment supply, and wetland vertical accretion. Human activities in watersheds have significantly altered sediment delivery from the landscape to the coastal ocean, with declines along much of the U.S. East Coast. Tidal wetlands in coastal systems with low sediment supply may have limited ability to keep pace with accelerating rates of sea‐level rise (SLR). Here, we show that rates of vertical accretion and carbon accumulation in nine tidal wetland systems along the U.S. East Coast from Maine to Georgia can be explained by differences in the rate of relative SLR (RSLR), the concentration of suspended sediments in the rivers draining to the coast, and temperature in the coastal region. Further, we show that rates of vertical accretion have accelerated over the past century by between 0.010 and 0.083 mm yr−2, at roughly the same pace as the acceleration of global SLR. We estimate that rates of carbon sequestration in these wetland soils have accelerated (more than doubling at several sites) along with accelerating accretion. Wetland accretion and carbon accumulation have accelerated more rapidly in coastal systems with greater relative RSLR, higher watershed sediment availability, and lower temperatures. These findings suggest that the biogeomorphic feedback processes that control accretion and carbon accumulation in these tidal wetlands have responded to accelerating RSLR, and that changes to RSLR, watershed sediment supply, and temperature interact to determine wetland vulnerability across broad geographic scales.

Spatiotemporal heterogeneity correction in land ecosystem services and its value assessment: a case study of the Loess Plateau of China.

The considerable variation in structures and functions of different ecosystems leads to highly variable ecosystem service values (ESVs). Consequently, the accurate quantification of ESVs can better assess and reflect impacts of land use and cover changes (LUCC) on ecosystem services. In the land use simulations of this study, a CA-Markov model was chosen and nine factors affecting land use change were evaluated, followed by the construction of a multi-criteria evaluation method to simulate land use scenarios between 2025 and 2030 on the Loess Plateau. Six key ecological indicators (economy, water production, net primary plant productivity, habitat quality, accessibility, and soil conservation) were used to correct for spatiotemporal heterogeneity within the terrestrial ESV equivalent weight table for China to obtain an ESV equivalent weight factor table that is applicable to the Loess Plateau. Using the newly corrected table, ESVs for the Loess Plateau region were estimated between 1995 and 2030, and the impacts of LUCC on ESVs were analyzed. The Kappa values for the 2015 land use simulation results were 0.80 and 0.83, which were greater than 0.75, indicating that the CA-Markov model simulations were accurate. Throughout the study period, the largest increases in land use type area were for built-up areas and forest lands, with built-up areas primarily derived from conversions of cultivated lands and grasslands, and forest land increases primarily coming from conversion of grasslands. ESVs increased overall by 933.97 × 108 yuan and 312.86 × 108 yuan from 1995 to 2018 and 2018 to 2030, respectively. The three largest contributors to ecosystem services among land use types were moderate grasses, shrublands, and dense grasslands. In conclusion, ESVs for the Loess Plateau steadily increased year by year from 1995 to 2030, indicating that ecological restoration projects played major roles in improving the stability and sustainability of the region's ecosystems.

COOPERATIVE MODELS OF DOING BUSINESS AND THEIR ROLE IN FARMING COMMUNITY DEVELOPMENT

A collective business model with a specific character, distinguishing it from personal and capital companies is the cooperative. The cooperative model has been refined over the years and has become one of the widespread models for managing factors of production and providing services to its members in almost all economic sectors and countries around the world. A cooperative is a voluntary association of natural persons who, through mutual assistance and cooperation under equal responsibility and rights, transfer part of their functions to a common enterprise. Co-operation has proven to be a successful business model for building joint production facilities for processing the primary plant and animal products of farmers, thus creating additional income for them. Based on the broad scope of the subject, I limit the purpose of development to highlight the advantages of the cooperative model for doing business in association (unification) of farmers on the example of several European countries. A main conclusion of the study is that cooperatives play a crucial role in the prosperity and socio-economic development of the farming community they serve and the rural areas in which they are located.

Effects of nutrient supply on leaf stoichiometry and relative growth rate of three stoloniferous alien plants.

Different nutrient supply brings about changes in leaf stoichiometry, which may affect growth rate and primary production of plants. Invasion of alien plants is a severe threat to biodiversity and ecosystem worldwide. A pot experiment was conducted by using three stoloniferous alien plants Wedelia trilobata, Alternanther philoxeroides and Hydrocotyle vulgaris to investigate effects of nutrient supply on their leaf stoichiometry and relative growth rate. Different nitrogen or phosphorus supply was applied in the experiment (N1:1 mmol L-1, N2:4 mmol L-1, and N3:8 mmol L-1, P1:0.15 mmol L-1, P2:0.6 mmol L-1 and P3:1.2 mmol L-1). Nitrogen and phosphorus concentrations in leaves of the three alien plants significantly increased with increase of nitrogen supply. With increase of phosphorus supply, nitrogen or phosphorus concentration of leaf was complex among the three alien plants. N:P ratio in leaf of the three alien plants subjected to different levels of nutrient supply was various. A positive correlation between relative growth rate and N:P ratio of the leaf is observed in W. trilobata and A. philoxeroides suffering from N-limitation. A similar pattern was not observed in Hydrocotyle vulgaris. We tentatively concluded that correlations between relative growth rate and N: P ratio of the leaf could be affected by species as well as nutrient supply. It is suggested that human activities, invasive history, local abundance of species et al maybe play an important role in the invasion of alien plants as well as relative growth rate.

Responses of aboveground and belowground net primary productivity of ephemeral plants to extreme drought and extreme precipitation

To examine the effects of extreme drought event and extreme precipitation event on productivity of ephemeral plant, we experimentally reduced and increased growing season precipitation amounts by 65% across four slope positions and aspects along sand dunes in the southern edge of the Gurbantünggüt Desert. The results showed that extreme drought significantly reduced aboveground net primary productivity (ANPP) and belowground net primary productivity (BNPP) by 48.8% and 13.7%, respectively, and that extreme precipitation significantly increased ANPP and BNPP by 37.9% and 23.2%, respectively. The sensitivity of ANPP (0.26 and 0.21 g·m-2·mm-1) to extreme drought and extreme precipitation was significantly higher than that of BNPP (0.02 and 0.03 g·m-2·mm-1). In addition, ANPP (24.22 g·m-2) and BNPP (5.77 g·m-2) on the east side of sand dune were significantly increased by 29.7% and 71.7% compared with those on the west side. There was no significant difference in the sensitivity of ANPP and BNPP to precipitation change among different slope positions and aspects.

Networking to reduce microbial risk in foods

Networking to reduce microbial risk in foods

Combined effects of warming and drought on plant biomass depend on plant woodiness and community type: a meta-analysis.

Global warming and precipitation extremes (drought or increased precipitation) strongly affect plant primary production and thereby terrestrial ecosystem functioning. Recent syntheses show that combined effects of warming and precipitation extremes on plant biomass are generally additive, while individual experiments often show interactive effects, indicating that combined effects are more negative or positive than expected based on the effects of single factors. Here, we examined whether variation in biomass responses to single and combined effects of warming and precipitation extremes can be explained by plant growth form and community type. We performed a meta-analysis of 37 studies, which experimentally crossed warming and precipitation treatments, to test whether biomass responses to combined effects of warming and precipitation extremes depended on plant woodiness and community type (monocultures versus mixtures). Our results confirmed that the effects of warming and precipitation extremes were overall additive. However, combined effects of warming and drought on above- and belowground biomass were less negative in woody- than in herbaceous plant systems and more negative in plant mixtures than in monocultures. We further show that drought effects on plant biomass were more negative in greenhouse- than in field studies, suggesting that greenhouse experiments may overstate drought effects in the field. Our results highlight the importance of plant system characteristics to better understand plant responses to climate change.