More Like this

1. Regional Assessment of Carbon Pool Response to Intensive Silvicultural Practices in Loblolly Pine Plantations

   https://doi.org/10.3390/f13010036  

   Vogel, Jason G.; Bracho, Rosvel; Akers, Madison; Amateis, Ralph; Bacon, Allan; Burkhart, Harold E.; Gonzalez-Benecke, Carlos A.; Grunwald, Sabine; Jokela, Eric J.; Kane, Michael B.; et al (January 2022, Forests)

   Tree plantations represent an important component of the global carbon (C) cycle and are expected to increase in prevalence during the 21st century. We examined how silvicultural approaches that optimize economic returns in loblolly pine (Pinus taeda L.) plantations affected the accumulation of C in pools of vegetation, detritus, and mineral soil up to 100 cm across the loblolly pine’s natural range in the southeastern United States. Comparisons of silvicultural treatments included competing vegetation or ‘weed’ control, fertilization, thinning, and varying intensities of silvicultural treatment for 106 experimental plantations and 322 plots. The average age of the sampled plantations was 17 years, and the C stored in vegetation (pine and understory) averaged 82.1 ± 3.0 (±std. error) Mg C ha−1, and 14.3 ± 0.6 Mg C ha−1 in detrital pools (soil organic layers, coarse-woody debris, and soil detritus). Mineral soil C (0–100 cm) averaged 79.8 ± 4.6 Mg C ha−1 across sites. For management effects, thinning reduced vegetation by 35.5 ± 1.2 Mg C ha−1 for all treatment combinations. Weed control and fertilization increased vegetation between 2.3 and 5.7 Mg C ha−1 across treatment combinations, with high intensity silvicultural applications producing greater vegetation C than low intensity (increase of 21.4 ± 1.7 Mg C ha−1). Detrital C pools were negatively affected by thinning where either fertilization or weed control were also applied, and were increased with management intensity. Mineral soil C did not respond to any silvicultural treatments. From these data, we constructed regression models that summarized the C accumulation in detritus and detritus + vegetation in response to independent variables commonly monitored by plantation managers (site index (SI), trees per hectare (TPH) and plantation age (AGE)). The C stored in detritus and vegetation increased on average with AGE and both models included SI and TPH. The detritus model explained less variance (adj. R2 = 0.29) than the detritus + vegetation model (adj. R2 = 0.87). A general recommendation for managers looking to maximize C storage would be to maintain a high TPH and increase SI, with SI manipulation having a greater relative effect. From the model, we predict that a plantation managed to achieve the average upper third SI (26.8) within our observations, and planted at 1500 TPH, could accumulate ~85 Mg C ha−1 by 12 years of age in detritus and vegetation, an amount greater than the region’s average mineral soil C pool. Notably, SI can be increased using both genetic and silviculture technologies. 

   more » « less
2. Grassland ecosystem recovery after soil disturbance depends on nutrient supply rate

   https://doi.org/10.1111/ele.13591  

   Seabloom, Eric W.; Borer, Elizabeth T.; Tilman, David; Mori, ed., Akira (September 2020, Ecology Letters)

   Abstract Human disturbances alter the functioning and biodiversity of many ecosystems. These ecosystems may return to their pre‐disturbance state after disturbance ceases; however, humans have altered the environment in ways that may change the rate or direction of this recovery. For example, human activities have increased supplies of biologically limiting nutrients, such as nitrogen (N) and phosphorus (P), which can reduce grassland diversity and increase productivity. We tracked the recovery of a grassland for two decades following an intensive agricultural disturbance under ambient and elevated nutrient conditions. Productivity returned to pre‐disturbance levels quickly under ambient nutrient conditions, but nutrient addition slowed this recovery. In contrast, the effects of disturbance on diversity remained hidden for 15 years, at which point diversity began to increase in unfertilised plots. This work demonstrates that enrichment of terrestrial ecosystems by humans may alter the recovery of ecosystems and that disturbance effects may remain hidden for many years. 

   more » « less
3. Soil Fertility and Plant Growth Enhancement Through Compost Treatments Under Varied Irrigation Conditions

   https://doi.org/10.3390/agriculture15070734  

   Suvendran, Subanky; Acevedo, Miguel F; Smithers, Breana; Walker, Stephanie J; Xu, Pei (April 2025, Agriculture)

   Global challenges such as soil degradation and water scarcity necessitate sustainable agricultural practices, particularly in regions where saline water is increasingly used for irrigation. This study investigates the effects of four compost treatments, including surface-applied mulch compost (MC), Johnson–Su biologically active compost incorporated into soil (JCI), mulch compost incorporated into soil (MCI), and no compost as control (NC), on soil fertility, microbial activity, and Capsicum annuum (chili pepper) growth. Greenhouse experiments were conducted using soil from two different sites (New Mexico State University’s (NMSU) agricultural research plots and agricultural field-testing site at the Brackish Groundwater National Desalination Research Facility (BGNDRF) in Alamogordo, New Mexico) and two irrigation water salinities (brackish at ~3000 µS/cm and agricultural at ~800 µS/cm). The Johnson–Su compost treatment demonstrated superior performance, due to its high soil organic matter (41.5%), nitrate (NO3−) content (82.5 mg/kg), and phosphorus availability (193.1 mg/kg). In the JCI-treated soils, microbial biomass increased by 40%, and total microbial carbon reached 64.69 g/m2 as compared to 64.7 g/m2 in the NC. Plant growth parameters, including chlorophyll content, root length, and wet biomass, improved substantially with JCI. For instance, JCI increased plant height by 20% and wet biomass by 30% compared to NC treatments. The JCI treatment also effectively mitigated soil salinity, reducing Na+ accumulation by 60% and Cl− by 70% while enhancing water retention and soil structure. Principal Component Analysis (PCA) revealed a distinct clustering of JCI treatments, demonstrating its ability to increase nutrient retention and minimize salinity stress. These results indicate that biologically active properties, such as fungi-rich compost, are critical to providing an effective, environmentally resilient approach for enhancing soil fertility and supporting sustainable crop production under brackish groundwater irrigation, particularly in regions facing freshwater scarcity. 

   more » « less
4. Land Use Change Alters Soil Organic Carbon: Constrained Global Patterns and Predictors

   https://doi.org/10.1029/2023EF004254  

   Huang, Xingzhao; Ibrahim, Muhammed Mustapha; Luo, Yiqi; Jiang, Lifen; Chen, Ji; Hou, Enqing (May 2024, Earth's Future)

   Abstract Land use change (LUC) alters the global carbon (C) stock, but our estimation of the alteration remains uncertain and is a major impediment to predicting the global C cycle. The uncertainty is partly due to the limited number and geographical bias of observations, and limited exploration of its predictors. Here we generated a comprehensive global database of 5,980 observations from 790 articles. The number of sites evaluated is at least seven times larger than in previous meta‐analyses. Our constrained estimates of different LUC's effects on soil organic C (SOC) and their variations across global climates reveal underestimation/overestimation in previous estimates. Converting forests and grasslands to croplands reduced SOC by 24.5% ± 1.53% (−11.03 ± 1.06 Mg ha⁻¹) and 22.7% ± 1.22% (−8.09 ± 0.67 Mg ha⁻¹), while 28.0% ± 1.56% (4.46 ± 0.42 Mg ha⁻¹) and 33.5% ± 1.68% (5.8 ± 0.38 Mg ha⁻¹) increases, respectively, were obtained in the reverse processes. Converting forests to grasslands decreased SOC by 2.1% ± 1.22% (−1.13 ± 0.44 Mg ha⁻¹), while the reverse process increased SOC by 18.6% ± 1.73% (3.31 ± 0.51 Mg ha⁻¹). Modeled relative importance of 10 drivers of LUC's impact on SOC revealed that higher initial SOC (iSOC) does not solely determine SOC loss in SOC‐negative LUC scenarios as previously proposed. Across four decades, reconverting croplands to forests and grasslands recovered only 49.5% (6.1 ± 0.51 Mg ha⁻¹) and 75.3% (7.0 ± 0.38 Mg ha⁻¹) of the iSOC, respectively, indicating the need for protecting C‐rich ecosystems. Our global data set advances information on LUC's effect on SOC and can be valuable to constrain Earth system models to reliably estimate global SOC stocks and plan climate change mitigation strategies. 

   more » « less
5. Assessing capacitance soil moisture sensor probes’ ability to sense nitrogen, phosphorus, and potassium using volumetric ion content

   https://doi.org/10.3389/fagro.2024.1346946  

   Stroobosscher, Zoë J; Athelly, Akshara; Guzmán, Sandra M (February 2024, Frontiers in Agronomy)

   Accurate and near real-time volumetric soil water and volumetric ion content (VIC) measurements can both inform precise irrigation scheduling and aid in fertilizer management applications in cropping systems. To assist in the monitoring of these measurements, capacitance-based soil moisture probes are used in agricultural best management practice (BMP) programs. However, the ability of these sensors to detect nutrients in the soil sourced from fertilizers is not well understood. The objective of this study was to evaluate the sensitivity of a capacitance-based soil moisture probe in detecting Nitrogen (N), Phosphorous (P), and Potassium (K) movement in the soil. To achieve this, a laboratory-based setup was established using pure sand soil cores. Raw soil moisture and VIC probe readings from the cores were contrasted across multiple N, P, and K rates. The N treatments applied were rates of 0, 112, 168, and 224 kg/ha; for P, were 0, 3.76, and 37.6 kg/ha, and for K were 0, 1.02, 1.53, and 2.04 kg/ha. Each nutrient was evaluated separately using a randomized complete block design experiment with three replications for N and K, and 5 replications for P. The impact of each nutrient rate on the sensitivity of VIC readings was determined by evaluating differences in three points of the time series, including the observed maximum point, inflection point, and convergence value as well as the time of occurrence of those points over a 24-hour period. These points were assessed at depths 5, 15, 25, 35, 45, and 55 cm. The findings of this study highlight the capacitance-based soil moisture probes’ responsiveness to changes in all K rates at most depths. However, its sensitivity to changes in N and P rates is comparatively lower. The results obtained in this study can be used to develop fertilizer management protocols that utilize K movement as the baseline to indirectly assess N and P, while helping to inform those who currently use the probe which nutrients the probe may be detecting. The probes’ readings could be incorporated into decision support systems for irrigation and nutrient management and improve control systems for precision water and nutrient management. 

   more » « less